1.

If `y sqrt(1-x^2)+x sqrt(1-y^2)=1`. Prove that `dy/dx=-sqrt((1-y^2)/(1-x^2))`

Answer» We have `xsqrt(1-y^(2))+ysqrt(1-x^(2))=1." …(i)"`
Putting `x = sin theta and y = cos phi` in (i), we get
`sin theta cos phi+cos theta sin phi=1`
`rArr sin(theta+phi)=1`
`rArr (theta+phi)=sin^(-1)(1)`
`rArr sin^(-1)x+sin^(-1)y=(pi)/(2)." ...(ii)"`
On differentiating both sides of (ii) w.r.t. x, we get
`(1)/(sqrt(1-x^(2)))+(1)/(sqrt(1-y^(2))).(dy)/(dx)=0.`
`therefore (dy)/(dx)=-sqrt((1-y^(2))/(1-x^(2))).`


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