Question

tan theta=7/24, sin theta<0 Find cos (2theta)

Answer 1

to find the third side use pythagoras

Answer 2

thank you... for helping

Answer 3

25?

Answer 4

yup

Answer 5

now you can find cos theta

Answer 6

for cos (2 theta) use angle formula

Answer 7

what is angle formula?

Answer 8

not sure how to do it with the 2

Answer 9

\[\cos(2\Theta) = \cos ^{2} \Theta - \sin ^{2}\]

Answer 10

sin^2 theta

Answer 11

you can find sin theta from the triangle too

Answer 12

I have the equation - i don't know what to with that. Ultimately i need to find cos(2theta)

Answer 13

??

Answer 14

cos theta = 24/25
sin theta = 7/25

Answer 15

but where did the squared go?

Answer 16

You know that \[ \cos2\theta=\cos ^{2}\theta-\sin ^{2}\theta \] and Kanwar already gave you both cos and sin, so just substitute them into your formula above to get your answer for cos2theta.