Question

If A=60° and B=30° show that, cos (A-B) = cos A cos B + sin A sin B​

Answer 1

Answer:

cos 30° = √3/2

Step-by-step explanation:

A = 60° and B = 30°

cos(60°-30°) = cos 60°×cos 30° + sin 60° × sin 30°

cos 30°= 1/2 × √3/2+√3/2×1/2

cos 30°= √3/4+√3/4

cos 30°= 2√3/4

cos 30°= √3/2

LHS = RHS

since cos 30° = √3/2

Answer 2

Answer:

Given: A=60° and B =30° Now, LHS = Cos (A+B) ⇒ Cos (60° + 30°) ⇒ Cos (90°) ⇒ 0 [∵ cos 90° = 0] Now, RHS = Cos A Cos B – Sin A Sin B ⇒ cos(60°) cos(30°) – sin(60°) sin (30°) ⇒ 0 ∴ LHS = RHS Hence ProvedRead more on Sarthaks.com - https://www.sarthaks.com/929176/if-a-60and-b-30-verify-that-cos-a-b-cosacosb-sinasinb?show=929182#a929182