tanθ⼀2-1⼀(tanθ⼀2)=-2⼀tanθ

2025-06-23 08:03:13
推荐回答(2个)
回答1:

令a=θ/2

左边=tana-1/tana
=(tan²a-1)/tana
=1/[tana/(tan²a-1)]
=-2/[2tana/(1-tan²a)]
=-2/tan2a
=-2/tanθ=右边
命题得证

回答2:

令a=θ/2
左边=tana-1/tana
=(tan²a-1)/tana
=1/[tana/(tan²a-1)]
=-2/[2tana/(1-tan²a)]
=-2/tan2a
=-2/tanθ=右边