Question

比较cos11π/8与sin10π/9的大小,

Answer 1

cos(11π/8)=cos(π+3π/8)=-cos(3π/8)

=-sin(π/2-3π/8)=-sin(π/8)

sin(10π/9)=sin(π+π/9)=-sin(π/9)

由于π/8和π/9都在第一象限,且π/8>π/9,所以：

sin(π/8)>sin(π/9)

或：

-sin(π/9)>-sin(π/8)

所以：sin(10π/9)>cos(11π/8)