Hello I have just done the 2013 paper and i was just going through the marking schedule. This is what I wrote for for 3 b. (iii). 2013

So first of all i proved that the opposite angles of the quadrilateral HXKJ are equal.

Let angle JHX be x and angle HXK be y

Co -interior angles on parallel lines add up to 180.

∴ ∠HXK = 180-y

Angles on a straight line add up to 180

∴∠XKJ = 180-(180-y)

=y

Opposite angles are equal

In the same way we can prove that ∠HJK is y

Then i said that “we know that the quadrilateral HXKJ is a rhombus as we know that the opposite angles of a rhombus are equal”.

But in the answers it says

Since HJK = HXK = 120°, and JHX =

JKX = 60°, we have 2 pairs of cointerior

angles:

JKX and HXK show that HX // JK.

Hence HJKX is a parallelogram.

Also, since HX = XK (radii) and

opposite sides of a parallelogram are

equal,

HX = JK and XK = HJ, and hence

HJKX is a rhombus

This is an E answer. So my question is, that if you were marking the test and you saw my answer and compared it to the marking schedule what would you give it?

Its question 3 (iii) from the 2013 geometric paper