What is the Formula of Cos C + Cos D ?

Solution :

The formula of cos C + cos D is 2 cos(\(C + D\over 2\)) cos(\(C – D\over 2\)).

Example : Express cos \(4\theta\) + cos \(8\theta\) as a product.

Solution : We have,

cos \(4\theta\) + cos \(8\theta\) = 2 cos(\(8\theta + 4\theta\over 2\)) cos(\(8\theta – 4\theta\over 2\))

= 2 cos \(6\theta\) cos \(2\theta\)


Similar Formulas

What is the Formula of Sin C + Sin D ?

What is the Formula of Sin C – Sin D ?

What is the Formula of Cos C – Cos D ?

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