2sin^(2)B+4cos(alpha+B)sin n sin B+cos2(alpha+B)

2sin^(2)B+4cos(A+B)sin A sin B+cos2(A+B)=

"Show that :" 2 sin^(2) beta + 4 cos ( alpha + beta) sin alpha sin beta + cos2 (alpha + beta) = cos2 alpha

2sin^(2)beta+4cos(alpha+beta)sin alpha sin beta+cos2(alpha+beta)=

Prove that 2sin^(2)beta+4cos(alpha+beta)sin alpha sin beta+cos2(alpha+beta)=cos2 alpha

x=sqrt(a^2cos^2alpha+b^2sin^2alpha)+sqrt(a^2sin^2alpha+b^2cos^2alpha) then x^2=a^2+b^2+2sqrt(p(a^2+b^2)-p^2) , where p is equal to (a) a^2cos^2alpha+ b^2sin^2alpha (b) a^2sin^2alpha+b^2cos^2alpha (c) (1/2)(a^2+b^2+(a^2-b^2)cos2alpha) (d) (1/2)(a^2+b^2-(a^2-b^2)cos2alpha)