**Sin 2 Theta Formula**. Here we look at trigonometric formulae known as the double angle formulae. There are many options for solving trigonometry questions.

However, all the identities that follow are based on these sum and difference formulas. They are called so because it involves. There are many options for solving trigonometry questions.

### From these formulas, we also have the following identities for.

In trigonometry, tangent half-angle formulas relate the tangent of half of an angle to trigonometric functions of the entire angle.

But in the cosine formulas, + on the left becomes − on the right; and vice-versa. Since these identities are proved directly from geometry, the student is not normally required to master the proof. There are many options for solving trigonometry questions.