`y = asintheta-bcostheta`
`x = acostheta+bsintheta`
`=>dx/(d theta) = -asintheta+bcostheta`
`=>dy/(d theta) = `
`:.dy/dx = dy/(d theta)*(d theta)/dx = (acostheta+bsintheta)/(-asintheta+bcostheta)`
`=>dy/dx = x/(-y)`
`=>(d^2y)/dx^2 = (-y + xdy/dx)/y^2`
`=>y^2(d^2y)/dx^2-xdy/dx+y =0`