Question

cos(2a)
(picture)

Answer 1

\[\cos \theta = \frac{ adjacent }{ hypotenuse }\]

Answer 2

would I just multiply cos(a) by 2 then?

Answer 3

it says the correct answer is 161/289

Answer 4

Im finding the cos of 16/15?

Answer 5

Use the formula:
cos(2x) = 2cos^2(x) - 1

So find the hypotenuse first. h^2 = 8^2 + 15^2. So h = ?

Answer 6

\[\sqrt{289}\]

Answer 7

Yes and sqrt(289) = 17

Now find cos(a) = adjacent / hypotenuse = 15 / 17

Put it in the equation cos(2a) = 2(cos(a))^2 - 1

Answer 8

Well?

Answer 9

ok i figured it out thank you