Question

根号下(1+cosα)/(1-cosα)-根号下(1-cosα)/(1+cosα)=-2/tanα求α取值范围

Answer 1

√[(1+cosα)/(1-cosα)]-√[(1-cosα)/(1+cosα)]

=(1+cosα)/|sinα|-(1-cosα)/|sinα|

=2cosα/|sinα|

2cosα/|sinα|=-2/tanα

sinα