Question

(a) If tan² A = 1 + 2tan² B, prove that cos² B = 2cos² A​

Answer 1

Explanation:

Note:

tanA=sinA/CosA i.e tan^2A=sin^2A/cos^2A

tanB=sinB/cosB

cos^2A+sin^2A=1

cos^2B+sin^2B=1

I hope this helps.