Question

Вычислить: а)sin159cos39+sin39cos21 б)7tg21+7tg24/1-tg21tg24

Answer 1

$1)Sin159^{0} Cos39^{0}+Sin39^{0}Cos21^{0}=Sin(180^{0}-21^{0})Cos39^{0}+Sin39^{0}Cos21^{0}=Sin21^{0}Cos39^{0}+Sin39^{0}Cos21^{0}=Sin(21^{0}+39^{0} )=Sin60^{0}=\frac{\sqrt{3} }{2}$

$2)\frac{7tg21^{0}+7tg24^{0}}{1-tg21^{0} tg24^{0}}=\frac{7(tg21^{0}+tg24^{0}}{1-tg21^{0}tg24^{0}}=7tg(21^{0}+24^{0} )=7tg45^{0}=7*1=7$