Question

What is the exact value of cos(2 sin^-1 (1/3))

Answer 1

\(sin^{-1}(1/3)=?\)

Answer 2

well don't you have to draw a triangle?

Answer 3

so 1^2 + b^2 = 3^2
so b=2sqrt2

Answer 4

then?? that is the side, not the angle.

Answer 5

you don't need to find the angle

Answer 6

ok thats what i thought

Answer 7

:)

Answer 8

\[\cos(2\theta)=\cos^2(\theta)-\sin^2(\theta)\]

Answer 9

then use your triangle

Answer 10

and that is a trig identity?

Answer 11

of a double angle

Answer 12

yes it is a trig identity

Answer 13

thanks

Answer 14

can you get the answer now?

Answer 15

yup it is 7/9

Answer 16

thank you so much

Answer 17

good