Porisma

A hint to get started

Trace a moving midpoint locus from tangent intercepts

For x=t2x=t^2, y=2/ty=2/t:

(i) Find and simplify the tangent equation at (p2,2/p)(p^2,2/p).

(ii) Hence find Q and R where that tangent meets the x- and y-axes, respectively.

(iii) Find a Cartesian equation for the locus of the midpoint of QR as p varies.

[2011/9740/I/3]

CJC · Lecture · Example 10

Parameterise the midpoint itself, then eliminate p from those two new coordinates.

Read the worked solution