cos585°/tan495°+sin690°的值是多少?
问题描述：
cos585°/tan495°+sin690°的值是多少?
答
cos585°=cos(585°-360°)=cos225°= -cos45°= -√2 /2tan495°=tan(135°+360°)=tan135°= -1而sin690°=sin(720°-30°)=sin(-30°)= -0.5所以cos585°/tan495°+sin690°=(-√2 /2) / (-1) -0.5=√2 /2 -0.5=(...