Prove 2SinAsinB =cos(A-B)-cos(A+B)
Right side of the equation:cos ( A - B ) - cos ( A + B ) == cos A cos B + sin A sin B - ( cos A cos B - sin A sin B ) == cos A cos B + sin A sin B - cos A cos B + sin A sin B == 2 sin A sin B - left side of the equation ( correct )
