Помогите срочно нужно

Question

Помогите срочно нужно

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Answer 1

(1+tg(a))-(1-tg(a))/(1-tg(a))*(1+tg(a))=tg2(a)=

=2tg(a)/1-tg^2(a)=tg2(a)=

=2-tg^2(a)+2tg^2(a)/1-tg(a)=

2-tg^2(a)+2tg^2(a/1-tg(a)=
=2tg(a)=tg2(a)