What is the formula of cos 3 x ?

Nathaly Rivers

Nathaly Rivers

Answered

2022-12-29

What is the formula of cos 3 x ?

Answer & Explanation

mosellasv2

mosellasv2

Expert

2022-12-30Added 4 answers

We know that,
cos A + B = cos A cos B - sin A sin B
Using the aforementioned property, we get
cos 3 x = cos 2 x + x
cos 3 x = cos 2 x cos x - sin 2 x sin x
cos 3 x = 2 cos 3 x - cos x - 2 sin 2 x cos x
cos 3 x = 2 cos 3 x - cos x - 2 1 - cos 2 x cos x
cos 3 x = 2 cos 3 x - cos x - 2 cos x + 2 cos 3 x
cos 3 x = 4 cos 3 x - 3 cos x
Thus the formula cos 3 x = 4 cos 3 x - 3 cos x

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