π/40sin(a-π/4)=3/5 cos（a-π/4)=4/5【根据公式】sina=sin(a-π/4+π/4）=sin(a-π/4)*sinπ/4+cos（a-π/4）*cosπ/4=10分之7倍的根2y=cos（x-π/4）=sin[π/2-(x-π/4)]=sin(3/4π-x)=-sin(x-3/4π),s所有将sinx先向右移3/4π个单位，然后为x轴对称翻转
