1)dy/(y+3)=-tanxdx
d(y+3)/(y+3)=-sinxdx/cosx
d(y+3)/(y+3)=d(cosx)/cosx
积分:ln|y+3|=ln|cosx|+c1
因此有:|y+3|=c|cosx|
2) dy/e^4y=e^3xdx
积分:e^(-4y)/(-4)=e^(3x)/3+c1
e^(-4y)=c-4/3e^(3x)
得:y=-[ln(c-4/3*e^(3x)]/4
1)dy/(y+3)=-tanxdx
d(y+3)/(y+3)=-sinxdx/cosx
d(y+3)/(y+3)=d(cosx)/cosx
积分:ln|y+3|=ln|cosx|+c1
因此有:|y+3|=c|cosx|
2) dy/e^4y=e^3xdx
积分:e^(-4y)/(-4)=e^(3x)/3+c1
e^(-4y)=c-4/3e^(3x)
得:y=-[ln(c-4/3*e^(3x)]/4