`(cos^2(pi/4-A)-sin^2(pi/4-A))/(cos^2(pi/4+A)+sin^2(pi/4+A)=)`

cos(pi/4-A)-sin(pi/4+A)=0

sin(pi/4+A).sin(pi/4-A)=1/2 cos2A

Evaluate sin^2(pi/4)+sin^2 (3pi/4)+sin^2(5pi/4)+sin^2(7pi/4)

cos(pi/4-A)cos(pi/4-B)-sin(pi/4-A)sin(pi/4-B)=sin(A+B)

Prove that, cos^(2) (pi/4) + sin^(2) (3pi/4) + sin^(2) (5pi/4) + sin^(2)(7pi/4) = 2 .

(sec^(2)(pi)/(4)-cot^(2)(pi)/(4))/(sin^(2)(pi)/(3)+cos^(2)(pi)/(6))+(sin^(2)(pi)/(2)-cos^(2)(pi)/(3))/((1)/(4)tan^(2)(pi)/(6))=9(2)/(3)

Prove that: cos(pi/4-A)cos(pi/4-B)-sin(pi/4-A)sin(pi/4-B)="sin"(A+B)

Prove that cos(pi/4-x)cos(pi/4-y)-sin(pi/4-x)sin(pi/4-y)=sin(x+y)

cos(pi/4-x)cos(pi/4-y)-sin(pi/4-x)sin(pi/4-y)=sin(x+y)

Prove that: cos(pi/4-x)cos(pi/4-y)-sin(pi/4-x)sin(pi/4-y)=sin(x+y)