Question

преобразуйте в произведение

Answer 1

1) $tg20+tg70=sin20/cos20+sin70/cos70=frac{sin(20+70)}{cos20*cos70} =frac{1}{0.5(cos50+cos90)} =frac{2}{cos50} =2sec50$

2) $(1-cosa)-sina=2sin^2frac{a}{2} -sina=2sin^2frac{a}{2}-2sinfrac{a}{2} *cosfrac{a}{2}=2sin frac{a}{2}(sinfrac{a}{2}-cos frac{a}{2})$

3) $frac{2sin15*cos10}{2sin15*sin10} =frac{cos10}{sin10} =ctg10$

$sin25+sin5=2sin(frac{25+5}{2}) *cos(frac{25-5}{2})$

$cos5-cos25=-2sinfrac{5+25}{2}sin frac{5-25}{2}$