" (a) "sin[(pi)/(4)+A]*sin[(pi)/(4)-A]=(1)/(2)cos2A

Prove that cos((pi)/(4)-x)cos((pi)/(4)+x)=(1)/(2)-sin^(2)x

Let P=(("cos"(pi)/(4),-"sin"(pi)/(4)),("sin"(pi)/(4),"cos"(pi)/(4))) and X=(((1)/(sqrt(2))),((1)/(sqrt(2)))) . Then P^(3)X is equal to

Let Q = [{: (cos ""(pi)/(4) , - sin""(pi)/(4)),(sin""(pi)/(4), cos""(pi)/(4)):}] and x = [{:((2)/(sqrt(2))),((1)/(sqrt(2))):}] then Q^(3) x is equal to

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

sin (pi/2) = 2 sin(pi/4) cos (pi/4)

Prove that (i) "sin " (7pi)/(12) " cos " (pi)/(2) - "cos " *(7pi)/(12) " sin " (pi)/(4) = (sqrt(3))/(2) (ii) " sin " (pi)/(4) " cos " (pi)/(2) + "cos"(pi)/(4) " sin " (pi)/(12) = (sqrt(3))/(2) (iii) " cos " (2pi)/(3) " cos " (pi)/(4) - " sin " (2pi)/(3) " sin " (pi)/(4) =(-(sqrt(3) +1))/(2sqrt(2))

Prove that : "sin"(pi)/(3) "tan"(pi)/(6) +"sin"(pi)/(2) "cos"(pi)/(3) =2 "sin"^(2)(pi)/(4) .

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