1)dy/(y+3)=-tanxdxd(y+3)/(y+3)=-sinxdx/cosxd(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+c1e^(-4y)=c-4/3e^(3x)得：y=-[ln(c-4/3*e^(...