Question

show that sin²75-cos²45=√3/4​

Answer 1

Answer:

W.K.T

cos(a+b)cos(a-b)=cos²b-sin²a

applying this,

suppose a=75 b=45

sin²75-cos²45 = -cos(75+45)cos(75-45)

                         =  -cos120cos30

                         =  -(-1/2)(√3/2)

                         =    √3/4

hence proved