Упростите выражение
(tg a+ctg a) (1+cos a) (1-cos a)

(1+cosα)(1-cosα)= 1-cos^2α=sin^2(α)
tgα+ctgα=sinα/cosα+cosα/sinα=1/(sinα*cosα)(sin^2α+cos^2α)=1/sinαcosα

1/(sinα*cosα)  *  sin^2α = sinα/cosα=tgα