Hello djmccabie(a)

The point P has parameter ; in other words, at P . So at P,

So the tangent at P has equation

i.e.

(b) This line meets the y-axis at B , where and

at B.

So the increase in from A to P is , and the increase in from P to B is . So by similar triangles, PB = 2PA.

Grandad