求方程所确定的隐函数的导数：y-sinx-cos(-y)=0

求方程所确定的隐函数的导数：
y-sinx-cos(-y)=0
【正确答案】：y'-cosx+sin(x-y)(1-y')=0，得y'=[cosx-sin(x-y)]/[1-sin(x-y)]