已知cos(x-y)cosx+sin(x-y)sinx=3/5,则cosy的值为

问题描述:

已知cos(x-y)cosx+sin(x-y)sinx=3/5,则cosy的值为

cos(x-y)cosx+sin(x-y)sinx=cos(x-y-x)=cos(-y)=cosy=3/5