Question

数学题，求详细解

Answer 1

解答 （1）sinπ tan(-2)=0 tan(-2)=0
(2) sin123° =sin(180°-123°)=sin33°>0
cos156°=-cos(180°-1156°)=-cos33°<0
可得sin123° cos156°<0

Answer 2

sinπ=0，sinπ·tan（-2）=0
123°、156°图像都在第二象限 ，所以sin123°＞0，cos156°＜0