# Thread: 3-i in trigonometric form

1. ## 3-i in trigonometric form

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.

2. What is the question?

3. can you show me how to find the angle (argument) please

4. like show me the steps

5. 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?

Polar - rectangular conversion

Also a calculator to use

Convert Rectangular to Polar Coordinates - Calculator

6. i think i get in now, if you do arctan(-1/3) you get -18.4, so you add 360 to -18.4 and then you get 341.6 degrees which is 5.96 radians.

Quick question, is it okay to leave the argument as degrees or does it have to be in radians?

7. Originally Posted by FedererForehand

Quick question, is it okay to leave the argument as degrees or does it have to be in radians?
Either is fine, radians is preffered in most walks of life.

Sometimes the question itself will say what is required.