| Identity Type | Formula |
|---|---|
| Sine | \[ \sin 2x = 2 \sin x \cos x \] |
| Cosine (Form 1) | \[ \cos 2x = \cos^2 x - \sin^2 x \] |
| Cosine (Form 2) | \[ \cos 2x = 2 \cos^2 x - 1 \] |
| Cosine (Form 3) | \[ \cos 2x = 1 - 2 \sin^2 x \] |
| Tangent | \[ \tan 2x = \frac{2 \tan x}{1 - \tan^2 x} \] |