Question

If tan²A = 1+ 2tan²B
Show: COS2B = 1+2 cos2A​

Answer 1

Explanation:

hello :

here is this idea :

tanA= sinA/cosA tanB= sinB/cosB

cos²A+sin²A =1 cos²B+sin²B =1

cos²A-sin²A=cos2A cos²B-sin²B=cos2B