Question

How do I solve for this?

Answer 1

Answer:
`cosx =- √( 1 - sin^2x)`

Explanation:

Generally speaking;
`cos^2x + sin^2x = 1`

rearranging this gives us all sorts of cool things.

for now, we will use:
`cosx = √( 1 - sin^2x)`

This however, is general.

In the third quadrant, cosine is negative. So cosx in QIII will be:

`cosx =- √( 1 - sin^2x)`

and thats the answer :)