Complex numbers z=-3-4i polar form Unicorn Meta Zoo #1: Why another podcast? Announcing the arrival of Valued Associate #679: Cesar ManaraExpressing $e^z$ where $z=a+bi$ in polar form.Polar form of Complex numbersConverting to polar formComplex number polar form equationWhy is e used for polar form of complex numbers?Show $-27$ in polar form.writing in polar form (complex numbers)Are all complex exponentials in polar form?Complex numbers polar form changeDifferentiating polar functions using complex numbers

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Complex numbers z=-3-4i polar form



Unicorn Meta Zoo #1: Why another podcast?
Announcing the arrival of Valued Associate #679: Cesar ManaraExpressing $e^z$ where $z=a+bi$ in polar form.Polar form of Complex numbersConverting to polar formComplex number polar form equationWhy is e used for polar form of complex numbers?Show $-27$ in polar form.writing in polar form (complex numbers)Are all complex exponentials in polar form?Complex numbers polar form changeDifferentiating polar functions using complex numbers










4












$begingroup$


$z=-3-4i$ . In polar form this becomes $[5, 233° ]$. The question then asks for $z^2$, so the polar form becomes $[25,466]$ However in the solution they did $466° -360° $ and I am unsure why they did this. Is it a rule that needs to be applied.










share|cite|improve this question











$endgroup$
















    4












    $begingroup$


    $z=-3-4i$ . In polar form this becomes $[5, 233° ]$. The question then asks for $z^2$, so the polar form becomes $[25,466]$ However in the solution they did $466° -360° $ and I am unsure why they did this. Is it a rule that needs to be applied.










    share|cite|improve this question











    $endgroup$














      4












      4








      4





      $begingroup$


      $z=-3-4i$ . In polar form this becomes $[5, 233° ]$. The question then asks for $z^2$, so the polar form becomes $[25,466]$ However in the solution they did $466° -360° $ and I am unsure why they did this. Is it a rule that needs to be applied.










      share|cite|improve this question











      $endgroup$




      $z=-3-4i$ . In polar form this becomes $[5, 233° ]$. The question then asks for $z^2$, so the polar form becomes $[25,466]$ However in the solution they did $466° -360° $ and I am unsure why they did this. Is it a rule that needs to be applied.







      complex-numbers polar-coordinates






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited 3 hours ago









      José Carlos Santos

      178k24139251




      178k24139251










      asked 3 hours ago









      user221435user221435

      285




      285




















          3 Answers
          3






          active

          oldest

          votes


















          4












          $begingroup$

          It's because$$cos(x-360^circ)=cos(x)text and sin(x-360^circ)=sin(x).$$






          share|cite|improve this answer









          $endgroup$












          • $begingroup$
            Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
            $endgroup$
            – user221435
            3 hours ago






          • 2




            $begingroup$
            We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
            $endgroup$
            – José Carlos Santos
            3 hours ago










          • $begingroup$
            Great, thank you
            $endgroup$
            – user221435
            3 hours ago










          • $begingroup$
            Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
            $endgroup$
            – Thomas Weller
            45 mins ago






          • 1




            $begingroup$
            @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
            $endgroup$
            – DreamConspiracy
            24 mins ago



















          2












          $begingroup$

          It is just to get the principal value of the angle, since if you rotate by an angle $466^circ$ you'll get to the same position as rotating $106^circ$ so we usually take the smallest angle that is needed to arrive at the desired position.



          The principal angle is an angle between $-180^circ$ and $+180^circ$






          share|cite|improve this answer











          $endgroup$




















            0












            $begingroup$

            The polar form of a complex number is given by a distance from the origin and an angle against the positive real axis ("$x$-axis"). Increasing or decreasing this angle by $360^circ$ will result in the same point. So adding or subtracting multiples of $360^circ$ from the angle component of a set of polar coordinates will not change which point those coordinates represent.



            By convention, we usually like this angle to be either in the range $[0^circ, 360^circ)$ or $(-180^circ, 180^circ]$. This is not a requirement by any means (unless explicitly stated in the exercise), but it's easier to tell by a glance what direction from the origin is represented by an angle of $270^circ$ than by $2430^circ$. So there is some merit to keeping the numbers small.






            share|cite|improve this answer









            $endgroup$













              Your Answer








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              3 Answers
              3






              active

              oldest

              votes








              3 Answers
              3






              active

              oldest

              votes









              active

              oldest

              votes






              active

              oldest

              votes









              4












              $begingroup$

              It's because$$cos(x-360^circ)=cos(x)text and sin(x-360^circ)=sin(x).$$






              share|cite|improve this answer









              $endgroup$












              • $begingroup$
                Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
                $endgroup$
                – user221435
                3 hours ago






              • 2




                $begingroup$
                We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
                $endgroup$
                – José Carlos Santos
                3 hours ago










              • $begingroup$
                Great, thank you
                $endgroup$
                – user221435
                3 hours ago










              • $begingroup$
                Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
                $endgroup$
                – Thomas Weller
                45 mins ago






              • 1




                $begingroup$
                @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
                $endgroup$
                – DreamConspiracy
                24 mins ago
















              4












              $begingroup$

              It's because$$cos(x-360^circ)=cos(x)text and sin(x-360^circ)=sin(x).$$






              share|cite|improve this answer









              $endgroup$












              • $begingroup$
                Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
                $endgroup$
                – user221435
                3 hours ago






              • 2




                $begingroup$
                We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
                $endgroup$
                – José Carlos Santos
                3 hours ago










              • $begingroup$
                Great, thank you
                $endgroup$
                – user221435
                3 hours ago










              • $begingroup$
                Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
                $endgroup$
                – Thomas Weller
                45 mins ago






              • 1




                $begingroup$
                @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
                $endgroup$
                – DreamConspiracy
                24 mins ago














              4












              4








              4





              $begingroup$

              It's because$$cos(x-360^circ)=cos(x)text and sin(x-360^circ)=sin(x).$$






              share|cite|improve this answer









              $endgroup$



              It's because$$cos(x-360^circ)=cos(x)text and sin(x-360^circ)=sin(x).$$







              share|cite|improve this answer












              share|cite|improve this answer



              share|cite|improve this answer










              answered 3 hours ago









              José Carlos SantosJosé Carlos Santos

              178k24139251




              178k24139251











              • $begingroup$
                Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
                $endgroup$
                – user221435
                3 hours ago






              • 2




                $begingroup$
                We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
                $endgroup$
                – José Carlos Santos
                3 hours ago










              • $begingroup$
                Great, thank you
                $endgroup$
                – user221435
                3 hours ago










              • $begingroup$
                Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
                $endgroup$
                – Thomas Weller
                45 mins ago






              • 1




                $begingroup$
                @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
                $endgroup$
                – DreamConspiracy
                24 mins ago

















              • $begingroup$
                Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
                $endgroup$
                – user221435
                3 hours ago






              • 2




                $begingroup$
                We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
                $endgroup$
                – José Carlos Santos
                3 hours ago










              • $begingroup$
                Great, thank you
                $endgroup$
                – user221435
                3 hours ago










              • $begingroup$
                Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
                $endgroup$
                – Thomas Weller
                45 mins ago






              • 1




                $begingroup$
                @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
                $endgroup$
                – DreamConspiracy
                24 mins ago
















              $begingroup$
              Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
              $endgroup$
              – user221435
              3 hours ago




              $begingroup$
              Usually I don't do this when I get the degree, why is it that in this case I needed to do this?
              $endgroup$
              – user221435
              3 hours ago




              2




              2




              $begingroup$
              We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
              $endgroup$
              – José Carlos Santos
              3 hours ago




              $begingroup$
              We don't need to do this, but we usually try to work with angles in the range $[0^circ,360^circ)$.
              $endgroup$
              – José Carlos Santos
              3 hours ago












              $begingroup$
              Great, thank you
              $endgroup$
              – user221435
              3 hours ago




              $begingroup$
              Great, thank you
              $endgroup$
              – user221435
              3 hours ago












              $begingroup$
              Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
              $endgroup$
              – Thomas Weller
              45 mins ago




              $begingroup$
              Which makes mathematicians very different from 3D modelers and animators, where it really matters if the object turns 1 time (360°) or 10 times (3600°). The end result is the same, but all the pictures in between will be different.
              $endgroup$
              – Thomas Weller
              45 mins ago




              1




              1




              $begingroup$
              @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
              $endgroup$
              – DreamConspiracy
              24 mins ago





              $begingroup$
              @ThomasWeller this is not exactly right. In the case above, the value measured in degrees is an angle, which should always be in the range given. In modelers and animators, the value given is something like angular distance (ie the some of the absolute values of changes in angle over time) which happens to be measured in the same units as angles (degrees, radians), but is not the same type of value. Because of this, applying trigonometric functions to angular distances is not meaningful (without further assumptions)
              $endgroup$
              – DreamConspiracy
              24 mins ago












              2












              $begingroup$

              It is just to get the principal value of the angle, since if you rotate by an angle $466^circ$ you'll get to the same position as rotating $106^circ$ so we usually take the smallest angle that is needed to arrive at the desired position.



              The principal angle is an angle between $-180^circ$ and $+180^circ$






              share|cite|improve this answer











              $endgroup$

















                2












                $begingroup$

                It is just to get the principal value of the angle, since if you rotate by an angle $466^circ$ you'll get to the same position as rotating $106^circ$ so we usually take the smallest angle that is needed to arrive at the desired position.



                The principal angle is an angle between $-180^circ$ and $+180^circ$






                share|cite|improve this answer











                $endgroup$















                  2












                  2








                  2





                  $begingroup$

                  It is just to get the principal value of the angle, since if you rotate by an angle $466^circ$ you'll get to the same position as rotating $106^circ$ so we usually take the smallest angle that is needed to arrive at the desired position.



                  The principal angle is an angle between $-180^circ$ and $+180^circ$






                  share|cite|improve this answer











                  $endgroup$



                  It is just to get the principal value of the angle, since if you rotate by an angle $466^circ$ you'll get to the same position as rotating $106^circ$ so we usually take the smallest angle that is needed to arrive at the desired position.



                  The principal angle is an angle between $-180^circ$ and $+180^circ$







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited 2 hours ago









                  J. W. Tanner

                  5,2001520




                  5,2001520










                  answered 3 hours ago









                  Fareed AFFareed AF

                  1,025214




                  1,025214





















                      0












                      $begingroup$

                      The polar form of a complex number is given by a distance from the origin and an angle against the positive real axis ("$x$-axis"). Increasing or decreasing this angle by $360^circ$ will result in the same point. So adding or subtracting multiples of $360^circ$ from the angle component of a set of polar coordinates will not change which point those coordinates represent.



                      By convention, we usually like this angle to be either in the range $[0^circ, 360^circ)$ or $(-180^circ, 180^circ]$. This is not a requirement by any means (unless explicitly stated in the exercise), but it's easier to tell by a glance what direction from the origin is represented by an angle of $270^circ$ than by $2430^circ$. So there is some merit to keeping the numbers small.






                      share|cite|improve this answer









                      $endgroup$

















                        0












                        $begingroup$

                        The polar form of a complex number is given by a distance from the origin and an angle against the positive real axis ("$x$-axis"). Increasing or decreasing this angle by $360^circ$ will result in the same point. So adding or subtracting multiples of $360^circ$ from the angle component of a set of polar coordinates will not change which point those coordinates represent.



                        By convention, we usually like this angle to be either in the range $[0^circ, 360^circ)$ or $(-180^circ, 180^circ]$. This is not a requirement by any means (unless explicitly stated in the exercise), but it's easier to tell by a glance what direction from the origin is represented by an angle of $270^circ$ than by $2430^circ$. So there is some merit to keeping the numbers small.






                        share|cite|improve this answer









                        $endgroup$















                          0












                          0








                          0





                          $begingroup$

                          The polar form of a complex number is given by a distance from the origin and an angle against the positive real axis ("$x$-axis"). Increasing or decreasing this angle by $360^circ$ will result in the same point. So adding or subtracting multiples of $360^circ$ from the angle component of a set of polar coordinates will not change which point those coordinates represent.



                          By convention, we usually like this angle to be either in the range $[0^circ, 360^circ)$ or $(-180^circ, 180^circ]$. This is not a requirement by any means (unless explicitly stated in the exercise), but it's easier to tell by a glance what direction from the origin is represented by an angle of $270^circ$ than by $2430^circ$. So there is some merit to keeping the numbers small.






                          share|cite|improve this answer









                          $endgroup$



                          The polar form of a complex number is given by a distance from the origin and an angle against the positive real axis ("$x$-axis"). Increasing or decreasing this angle by $360^circ$ will result in the same point. So adding or subtracting multiples of $360^circ$ from the angle component of a set of polar coordinates will not change which point those coordinates represent.



                          By convention, we usually like this angle to be either in the range $[0^circ, 360^circ)$ or $(-180^circ, 180^circ]$. This is not a requirement by any means (unless explicitly stated in the exercise), but it's easier to tell by a glance what direction from the origin is represented by an angle of $270^circ$ than by $2430^circ$. So there is some merit to keeping the numbers small.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 15 mins ago









                          ArthurArthur

                          123k7122211




                          123k7122211



























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