What is the value of $$cos^{2}(A/2)$$?
Using double angle formula, we know that $$cos(2\theta) = cos^2\theta - sin^2\theta$$
=> $$cos(2\theta) = cos^2\theta - (1 - cos^2\theta)$$
=> $$cos(2\theta) = 2cos^2\theta - 1$$
Replacing $$\theta$$ by $$\frac{A}{2}$$, we get :
=> $$cos A = 2cos^2(\frac{A}{2}) - 1$$
=> $$cos A + 1 = 2cos^2(\frac{A}{2})$$
=> $$\frac{(cos A + 1)}{2} = cos^2(\frac{A}{2})$$
=> Ans - (B)
Create a FREE account and get:
