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

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

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

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