What is the Formula of Cos C – Cos D ?

Solution :

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

Example : Express cos $$6\theta$$ – cos $$8\theta$$ as a product.

Solution : We have,

cos $$6\theta$$ – cos $$8\theta$$ = 2 sin($$6\theta + 8\theta\over 2$$) sin($$8\theta – 6 \theta\over 2$$)

= 2 sin $$7\theta$$ sin $$\theta$$

Similar Formulas

What is the Formula of Sin C + Sin D ?

What is the Formula of Cos C + Cos D ?

What is the Formula of Sin C – Sin D ?