Question

How do you find the exact value of cos2x using the double angle formula?

Answer 1

Find the value of cos 2x

Explanation:

Use the trig identity: cos (a + b) = cos a.cos b - sin a.sin b.
cos 2x = cos (x + x) = cos x.cos x - sin x.sin x =
Formula 1:
`cos 2x = cos^2 x - sin^2 x` (1)
Formula 2
`cos 2x = (1 - sin^2 x) - sin ^2 x = 1 - 2sin^2 x.` (2)
Formula 3.
`cos 2x = cos^2 x - (1 - cos^2 x) = 2cos^2 x - 1` (3)