Question

Find the exact value of the trigonometric function. (If an answer is undefined, enter UNDEFINED.)
cos 390°

Answer 1

hint:
cos(390)=cos(390-360)

Answer 2

\[\cos(x^o)=\cos(x^o+360^on) \text{ where n is an integer } \\ \sin(x^o)=\sin(x^o+360^on) \text{ where n is an integer }\]

Answer 3

I chose n=-1 since that would put us in the first rotation of a circle