解:两边分别对x求导,将y看为x函数,遇到单独的y时用y‘代替 ,(如果出现形如xy的情形时,则表示为(xy)'=y+xy' )
cosy-(xsiny)y' =cos(x+y)(1+y')
然后解出y' 就行了。即y'=[cosy-cos(x+y)]/[cos(x+y)+xsiny]
xcosy=sinxcosy+cosxsiny
cosy-y'xsiny=cosxcosy-y'sinxsiny -sinxsiny+y'cosxcosy
cosy-y' xsiny=cos(x+y)+y'cos(x+y)
cos(x+y)-cosy= -y'[cos(x+y)+xsiny]
y'= -[cos(x+y)-cosy]/[cos(x+y)+xsiny]
解:
xcosy=sin(x+y)
cosy-x(y')siny=(1+y')cos(x+y)
cosy-x(y')siny=cos(x+y)+(y')cos(x+y)
cosy-cos(x+y)=(y')cos(x+y)+x(y')siny
(y')[cos(x+y)+xsiny]=cosy-cos(x+y)
y'=[cosy-cos(x+y)]/[cos(x+y)+xsiny]
左右各求导,得:cosy-xsiny.(y')=cos(x+y)*(1+y'),合并同类项得:y'=(cosy-cos(x+y))/(cos(x+y)+xsiny)