The inquiry questions in mathematical problems are as follows

I think this topic should mean this:

1. If p is on an ellipse, the tangent equation of p is xx0/a2+yy0/b2= 1.

2. If P is not on the ellipse, the tangent equation can be obtained by tangency of the ellipse with P..

In fact, whether P is on the ellipse or not, the tangent equation is actually the same.

For example:

1, p is on the ellipse, then x0*x0/a2+y0*y0/b2= 1.

Meanwhile, the tangent equation is assumed to be y-y0=K(x-x0).

The tangent equation obtained by substituting elimination k is xx0/a2+yy0/b2= 1.

2. If p is not on the ellipse, make the tangent of the ellipse through p..

Because the points on the ellipse satisfy x*x/a2+y*y/b2= 1.

And assume that the tangent equation is also y-y0=K(x-x0).

Then the tangent equation can still be obtained by eliminating k as xx0/a2+yy0/b2= 1.