Eureka! I have just found a truly shiny thing. A prized possession in my magpie collection of shiny resources.
A video that explains why CIRCLE THEOREMS are useful.
Hooray! I love circle theorems. I love the way you have to
visualise shapes inside a complex diagram, but once you've seen the
visual links, the actual calculations are not hard at all. They make for lots
of lovely "ohhhh, I get it" moments.
The only problem I have with teaching circle theorems is that I can never think of a practical use for them. But I've just found one: Calculating the distance of the visible horizon.
Here is the link: http://www.youtube.com/watch?v=VRvvtOAHDG0&feature=player_embedded
Its particularly good because the nice young man in the video explains why maths is so important to his job first, then gives you a lovely clear example of how to use the circle theorem that the angle between the tangent and a radius is 90 degrees.
The only problem is that I just taught that topic to y11 today. I wish I'd found it yesterday!