Question

If A+B + C = π, then prove that .
cos? A+ cos²B + cos²c = 1-2cosA.cosB.cosC
hence prove that
cos60=1/2?​

Answer 1

Step-by-step explanation:

Input the value as:

A=60°

B=60°

C=60°

3cos²60=1-2cos³60

2cos³60+3cos²60-1=0

(cos60+1)²(2cos60-1)=0

cos60=(-1) wrong

2cos60-1=0

cos60=1/2