Question

How do you find cos(t) if t is in the 3rd quadrant and tan(t)= 3?

Answer 1

`-1/sqrt10`

Explanation:

First we get cos t value in the first quadrant. For this compute `sec^2 t= 10` so that cos t= `1/sqrt10`. In the third quadrant it wouls be cos(t+180)= -cos t= `-1/sqrt10`