1.а)-ctgα·tg(-α)-sin²(-α)=-ctgα·(-tgα)-sin²α=ctgα·tgα-sin²α=
=1-sin²α=cos²α;
б)[(1/sin²α)-1]·tg²α=[(1-sin²α)/sin²α]·tg²α=(cos²α/sin²α)·tg²α=
=ctg²α·tg²α=1;
2.[cosα/(1-sinα)]-[cosα/(1+sinα)]=2tgα;
[cosα/(1-sinα)]-[cosα/(1+sinα)]=[cosα·(1+sinα)-cosα(1-sinα)]/[(1-sinα)(1+sinα)]=
=(cosα+cosα·sinα-cosα+cosα·sinα)/(1-sin²α)=
=2cosα·sinα/cos²α=2sinα/cosα=2tgα;
2tgα=2tgα;