Hello thereddevilsCorrect! is not perpendicular to .

Suppose the length of is .

Then, using the formula, write down the areas of 's and . (Hint: the area of .)

Then consider these two triangles as though their bases lay along the line . So they have a common height. So the ratio of their areas is the same as the ratio of the lengths of their bases which is C" alt="BDC" />.

Then use your first two areas, and you're there.

(Incidentally, although you're told that , it doesn't have to be, provided it is bisected by .)

Grandad