tan22.5/1-tan^22.特别是1-tan^22.5那里,我不懂
问题描述：
tan22.5/1-tan^22.特别是1-tan^22.5那里,我不懂
答
tan22.5/1-tan^2 22.5
=(sin22.5/cos22.5)/(1-sin^2 22.5/cos^2 22.5)
=(sin22.5cos22.5)/(cos^2 22.5-sin^2 22.5)
=(sin45/2)/cos45=1/2