Question

Find cos theta and sin theta, theta in (0, pi/2) for which cos 2theta = -1/9

Answer 1

Do we have a domain to work with?

Answer 2

"theta in (0, pi/2)"

Answer 3

got ya

Answer 4

\[\cos (x)=\sqrt{\frac{8}{18}}\] ?

Answer 5

Duckking the sign this time? :-)

Answer 6

Yes, that's right...

Answer 7

How about sin?

Answer 8

\[\sqrt{\frac{10}{18}}\]