求此二阶微分方程的解法y''^2=1/4*(100-x)^2 -[y'/2(100-x)]^2 当我将y'设为z之后,y
y''²=(100-x)²/4-y'²(100-x)²/4==>4y''²=(1-"}}}'>

2个回答

  • ∵y''²=(100-x)²/4-[y'(100-x)/2]²

    ==>y''²=(100-x)²/4-y'²(100-x)²/4

    ==>4y''²=(1-y'²)(100-x)²

    ==>2y''=±(100-x)√(1-y'²)

    ==>2dy'/√(1-y'²)=±(100-x)dx

    ==>2arcsin(y')=2C1±(100x-x²/2) (C1是积分常数)

    ==>y'=sin[C1±(50x-x²/4)]

    ==>y=∫sin[C1±(50x-x²/4)]dx+C2 (C1是积分常数)

    ∴原方程的通解是y=∫sin[C1±(50x-x²/4)]dx+C2 (C1,C2是积分常数).