Originally Posted by

**Tutu** Hi I seem to not understand what the question is asking.

If z=2cis(delta),

write -z* in polar form.

I understand how to do this, my -z* was -2cos(delta) + i2sin(delta)

This is the second quadrant, and since

the coordinates of z are (2cos(delta), 2sin(delta))

the coordinates of -z* are (-2cos(delta), 2sin(delta)),

Can I can safely say that from z to-z*, it is a rotation of pi/2 about the origin?

Thus, my answer will be 2cis( delta + pi/2 ).

However, the answer is 2cis(pi - delta), which I understand because it still refers to the second quadrant, but I really wonder what is wrong with my answer. Looking at the coordinates, isn't it a pi/2 rotation? Unless my coordinates are wrong..

Sorry also, could you help me with this, Express sin(delta) - icos(delta) in polar form? The only thing I can gather is that the modulus equals to 1 and arctan(pi/2-delta).

Thank you so much!