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# Find the square root of a complex number system?

Updated: 4/28/2022

Wiki User

12y ago

Probably the best way is to change the complex number to its polar form, [or the A*eiΘ form] A is the magnitude or the distance from the origin to the point iin the complex plane, and Θ is the angle (in radians) measured counterclockwise from the positive real axis to the point. To find the square root of a number in this form, take the positive square root of the magnitude, then divide the angle by 2. Since there will always be 2 square roots for every number, to find the second root, add 2pi radians to the original angle, then divide by 2.

Take an easy example of square root of 4. Which we know is 2 and -2. OK so the magnitude is 4 and the angle is 0 radians. zero divided by 2 is zero, and the positive square root of 4 is 2. Now for the other square root. Add 2pi radians to 0, which is 2pi, then divide by 2, which is pi. pi radians [same as 180°] points in the negative real direction (on the horizontal), so we have ei*pi = -1 and then multiply by sqrt(4) = -2.

Try square root of i. i points straight up (pi/2 radians) with magnitude of 1. So the magnitude of the square root is still 1, but it points at pi/4 radians (45°). Converting back to rectangular gives you sqrt(2)/2 + i*sqrt(2)/2. The other square root will always point in the opposite direction [180° or pi radians]. So the other square root is at 225° or 5pi/4 radians, and the rectangular for this is -sqrt(2)/2 - i*sqrt(2)/2. Using FOIL (from Algebra) you can multiply it out like two binomials and you will get i when you square either of the two answers for square root.

Wiki User

12y ago