求xy-sin(πy^2)=0在(0,-1)的二阶导数.

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求xy-sin(πy^2)=0在(0,-1)的二阶导数.
求xy-sin(πy^2)=0在(0,-1)的二阶导数.

求xy-sin(πy^2)=0在(0,-1)的二阶导数.
y''=-(y'(x+2πycos(πy^2))-y(1+2πy'cos(πy^2)-2πysin(πy^2)*2πyy'))/(x+2πycos(πy^2))^2
=-(1/(2π)*(-2π)-(1-2π*1/(2π)-0))/(-2π)^2
=-(-1)/((2π)^2)
=1/4π^2

两边对x求导得
y+xy'-cos(πy^2)*2πy*y'=0
把(0,-1)代入得
-1-2πy'=0
y'=-1/(2π)
两边再对x求导得
y'+y'+xy''+sin(πy^2)*(2πy*y')^2-cos(πy^2)*2π(y')^2-cos(πy^2)*2πy*y''=0
把x=0,y=-1,y'=-1/(2π)代入
自己代入吧