Question

For z1 = 2cis120° and z2 = 4cis30°, find z1 · z2 in rectangular form

Answer 1

I'm not 100% sure but I'll give it my best shot

rcis(x) · rcis(y) = r^2 cis(x+y) (multiply the r's, add the thetas)

then from there, r*cis(a) = r[cos(a) + isin(a)], then you can simply evaluate cos and sin at the appropriate angles, and distribute the r to get back to rectangular notation

Answer 2

@mhchen would you mind double checking my work when you have a chance?