Question

Упростить cosα/ 1+cosα - cosα/ 1-cosα

Answer 1

cosα/(1+cosα)-cosα/(1-cosα)=[cosα*(1-cosα)-cosα(1+cosα)]/(1-cos²α)=
= cosα(1-cosα-1- cosα)/sin²α=-2cos²α/sin²α=-2ctg²α