cos squared theta minus sin square theta equal to 1 minus 10 squared theta by 1 + 10 squared theta prove the identity
Cos^2-Sin^2=1-Tan^2/1+Tan^2
Taking RHS, 1-Tan^2/1+Tan^2 ………..(i)
We Know that, Tan=SinCos, by putting in eq (i), we get
1-(Sin/Cos)^2/1+(SinCos)^2
1-(Sin^2/Cos^2/1+(Sin^2-Cos^2)
Cos2-Sin2Cos2Cos2+Sin2Cos2
Cos2-Sin2Cos2+Sin2
Cos2-Sin21
Cos2-Sin2=LHS
So, RHS=LHS