Question

已知sinx+cosy=1/3,siny+cosx=1/2,则sin(x-y)=

Answer 1

sinx+cosy=1/3,

siny+cosx=1/2

平方得

(sinx+cosy)^2=(1/3)^2,

(siny+cosx)^2=(1/2)^2

平方相加得

2+2sin(x+y)=1/9+1/4

题目有问题