This situation?
in a triangle ABC, AC=BC and angle ACB=40. The vertices A,B and C lie on the circumference of a cirlce. D is a point outside this circle such that DC is perpendicular to BC, BC=DC and the points B and D are on the same side of the line AC. DA cuts the circumference of the circle at E. Find the size of angle BCE.
any help would be great
There are lots of circle theorems. This is a link for them. I used the first one.
http://www.mathsrevision.net/gcse/pages.php?page=13