Question

Find the correct value to fill in the space below.

cos 50° = 2 cos^2 ____° -1

Answer 1

25°

Explanation:

Using the double angle trigonometric identity for cosine

• cos2x = 2cos²x - 1

Here 2x = 50° ⇒ x = 25°, thus

cos50° = 2cos²25° - 1

Answer 2

25.

Explanation:

Use the identity cos 2x = 2 cos^2 x - 1

So cos 50 = 2 cos^2 25 - 1

So the space = 25.