tan^2a =2tan^2b+1 求证 cos2a +sin^2b=0
问题描述：
tan^2a =2tan^2b+1 求证 cos2a +sin^2b=0
需要详解.
答
tan^2a +1=2（tan^2b+1) 所以1/cos^2a=2/ cos^2b
2cos^2a=cos^2b=1-sin^2b
1+cos2a=1-sin^2b cos2a +sin^2b=0