You have a great series of posts on Trapeziums here! I actually had completely forgotten about this topic from my geometry classes, but your posts do a remarkably good job of explaining the concept. This would be a good topic to introduce alongside the parallelogram, to show the contrast of 1 vs 2 sets of parallel sides.
Thanks for the kind words Shaun, I will do a series on parallellograms too in a while – June or July. Coming up next week, the inscribed angle theorem and cyclic quadrilaterals 🙂
CAT-holics 
You have a great series of posts on Trapeziums here! I actually had completely forgotten about this topic from my geometry classes, but your posts do a remarkably good job of explaining the concept. This would be a good topic to introduce alongside the parallelogram, to show the contrast of 1 vs 2 sets of parallel sides.
Thanks for the kind words Shaun, I will do a series on parallellograms too in a while – June or July. Coming up next week, the inscribed angle theorem and cyclic quadrilaterals 🙂
-J