3-i
my main problem is finding the angle, the book's full answer is square root of 10 cis 5.96 (radians) how do i get 5.96 radians?
im supposed to use arctan(y/x) but im getting it wrong.
for $\displaystyle x+yi$ then $\displaystyle \theta = \tan^{-1}\frac{y}{x}$ So in in your case $\displaystyle \theta = \tan^{-1}\frac{-1}{3}$
Do you have a calculator?
More reading
Polar - rectangular conversion
Also a calculator to use
Convert Rectangular to Polar Coordinates - Calculator