dy(1+tany)=(x^2+1)dx
dy+siny/cosy* dy=(x^2+1)dx
dy-d(cosy)/cosy=(x^2+1)dx
积分:y-ln|cosy|=x^3/3+x+C
代入y(0)=0,得:C=0
所以特解为 y-ln|cosy|=x^3/3+x
dy(1+tany)=(x^2+1)dx
dy+siny/cosy* dy=(x^2+1)dx
dy-d(cosy)/cosy=(x^2+1)dx
积分:y-ln|cosy|=x^3/3+x+C
代入y(0)=0,得:C=0
所以特解为 y-ln|cosy|=x^3/3+x