Question

If tan²A = 1+ 2tan²BShow: COS2B = 1+2 cos2A​

Answer 1

Answer:

Step-by-step explanation:

hello :

here is this idea :  

tanA= sinA/cosA          tanB= sinB/cosB

cos²A+sin²A =1              cos²B+sin²B =1  

cos²A-sin²A=cos2A            cos²B-sin²B=cos2B