Question

please anyone proof this problem​

Answer 1

cos^2a- sin^2 a = tan^2 b

cos 2a = tan^2b

2 cos^2 a - 1 = sec^2b -1

2 cos^2 a = 1/cos^2b.

2cos^2 a cos^2 b = 1

cos^2 b = 1/2 cos^2 a

cos^2 b - sin^2 b

cos 2b

2 cos^2b -1

2(1/2 cos^2 a). -1

sec^2 a - 1

tan^2 a