# Rect. and Polar with complex numbers

1. Apr 3, 2008

### krnhseya

1. The problem statement, all variables and given/known data

B= 4-j2. Find $$\sqrt{B}$$ in rectangular and polar notation.

2. Relevant equations

n/a

3. The attempt at a solution

i can figure out that in rectangular form by using the calculator and converting those back into polar form but how can i do this without calculator?

2. Apr 3, 2008

### chroot

Staff Emeritus
When you multiply two complex numbers together, their magnitudes are multiplied and their angles are added.

- Warren

3. Apr 3, 2008

### krnhseya

magnitude of B = sqrt(4^2 + (-2)^2)
and use tangent to find the angle.

but i am asked to find square root.

4. Apr 3, 2008

### chroot

Staff Emeritus
You're looking for a complex number, the square root of B. You know that if you multiply the square root of B by itself, you get B. Find the complex number that, when multiplied by itself (using the "rule" I have already given you), results in B.

- Warren

5. Apr 3, 2008

...?

6. Apr 3, 2008

### krnhseya

sorry but last 2 posts dont help me at all;
it's quite obvious that sqrt(b) ^2 = b...and i know how to find magnitude and angle once i get it in forms of X + yj

7. Apr 30, 2008