Hello misterriceman

Suppose that the orthocentre, O, has coordinates . Then we use the fact that the line joining the orthocentre to any vertex is perpendicular to the opposite side. So:

Gradient of OX =

Gradient of YZ =

So the product of these gradients is ; i.e.

(1)

In a similar way, using OZ and XY, we get:

(2)

Now solve the simultaneous equations (1) and (2) to find and . (Horrible numbers!) I make this:

and

I think you should check my working!

Grandad