For `alpha=pi/7` which of the following hold (s) good?

If sin (x + 20^(@)) = 2 sin x cos 40^(@), where x in (0.pi //2), then which of the following hold (s) good?

A function f is defined by f(x) = int_0^pi cos t cos(x-t)dt,0 <= x <= 2 pi then which of the following.hold(s) good?

A function f is defined by f(x) = int_0^pi cos t cos(x-t)dt,0 <= x <= 2 pi then which of the following.hold(s) good?

Let alpha, beta and gamma be some angles in the first quadrant satisfying tan(alpha + beta)=15//8 and "cosec" gamma = 17//8 , then which of the following hold(s) good ?

Let alpha, beta and gamma be some angles in the first quadrant satisfying tan(alpha+beta)=15//8 and cosec gamma = 17//8 , then which of the following hold(s) good ?

If b+c+,c+a,a+b are in H.P. then which of the following hold(s) good ?