A series of 12 programmes 5: Geometry I
Problem: In the cyclic quadrilateral ABCD, angle ABC = 63°. Find angle CDA. The tools for solving geometry problems are theorems. There are five circle theorems-none of them need to be proved but you do need to have a picture of them in your mind.
Presented by LAURIE BUXTON (Inner London Education Authority)
Books, Maths Help parts I and 2. £3.95 each from booksellers