Question

Prove that cos(a+b) = cos a cos b - sin a sin b

Answer 1

Answer:

How to prove cos (A+B) = cos A cos B - sin A sin B? Consider a right angle triangle ABC such that AC =3 cm, BC = 4 cm and AB = 5 cm, here <ACB is the right angle. So <A + <B = 180 -<C = 90 deg. ... Hence, cos (A+B) = cos A cos B - sin A sin B.

Step-by-step explanation:

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