不通过求值,比较下列各组三角函数值的大小

Cos(-47π/10)
=cos(13π/10-6π)
=cos13π/10
=-cos3π/10
Cos(-44π/9)
=cos(10π/9-6π)
=cos10π/9
=-cosπ/9
cos在第一象限是减函数
所以cos3π/10-cosπ/9
Cos(-47π/10)>Cos(-44π/9)
Sin508°
=sin(360+148)
=sin148
=sin(180-32)
=sin32
Sin144°
=sin(180-36)
=sin36
sin在第一象限是增函数
所以sin32