Помогите! Не понимаю! ​

Question

Помогите! Не понимаю! ​

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Answer 1

tg(2π/3)*cos(-π/3)/cos(7π/6)=tg(120°)*cos(-60°)/cos(210)=

=tg(180°-60°)*cos(-60°)/cos(180°+30°)=-tg(60°)*cos(60°)/(-cos(30°))=

=(-√3)*(1/2)/(-√3/2)=(-√3/2)/(-√3/2)=1.