Question

The equation of chord of contact y^2=4ax from the point (x1,y1)​

Answer 1

Consider the two points on the parabola are P(at12, 2at1) and Q (at22, 2at2).

Now write the equation of tangents at P and Q and find their point of intersection.

If they intersect at (x1,y1), then you will get x1 = at1t2 and y1 = a(t1 + t2).

Now write the distance formula for PQ and replace t1t2 by x1/a and (t1 + t2) by y1/a.

You will get the derived result.