The function of an angle i.e the angles and sides relationships is given by trigonometric functions. Sine, cosine, tangent, cotangent, Cos, Cosec are the trigonometric functions. We have different trigonometric values for these trigonometric functions for various angles like 30 0, 600 etc.

To classify the trigonometric functions, the angles of Sine, cosine and tangent are the primary ones.

**Cos2 theta formula**

**Cos 2 theta= 1 – sin2 theta**

## Examples of Cos squared theta formula

**Question** : What is the value of cos square x, if Sin x = ⅗?

Solution: **Cos 2 x = 1 – Sin2 x**

= 1 – (⅗)2

= 1 – 9/25

= (25 – 9) / 25

= 16/25

Cos x = 16/25 = 4/5