Question

Using the formula cos2 = 2cos2 - 1, find the value of cos30°, it is being given that cos60° = 1 2

Answer 1

Step-by-step explanation:

cos2x=2cos^2 x-1

cos60°=2cos^2 30°-1

1/2=2cos^2 30°-1

3/2=2cos^2 30°

3/4=cos^2 30°

root 3/2 = cos30°