What is the formula of cos 3x?

The formula for cos 3x is 4cos³(x)-3cos(x).

The cos 3x formula is a trigonometric identity that represents the cosine of three times an angle x as the cosine of the angle x. The formula goes as follows:

cos 3x = 4cos³(x)-3cos(x)

Cos 3x Derivation

The formula for cos(3x) can be derived using the triple-angle identity for cosine, which states that:

cos(3θ) = 4cos³(θ) − 3cos(θ)

In this formula, cos(θ) represents the cosine of the angle θ. Applying this identity to cos(3x), we substitute θ = x:

cos(3x) = 4cos³(x) − 3cos(x)

So, the formula for cos(3x) is 4cos³(x) − 3cos(x), which expresses the cosine of three times an angle in terms of the cosine of the angle itself.