比较下列各组中两个三角函数值的大小(1)sin(-320°)与sin700°(2)cos(17π/8)与cos(37π/9)

问题描述:

比较下列各组中两个三角函数值的大小(1)sin(-320°)与sin700°(2)cos(17π/8)与cos(37π/9)

sin(-320)=sin(-320+360)=sin40>0sin700=sin(700-2*360)=sin(-20)=-sin20sin700cos(17π/8)=cos(17π/8-2π)=cos(π/8)cos(37π/9)=cos(37π/9-4π)=cos(π/9)第一象限cos递减,π/8>π/9所以cos(17π/8)