# A Similarity problem

Hello there ,
http://img8.imageshack.us/img8/3118/circlem.jpg [Broken]

As you see the diameter = 5cm and AD = 4cm
the required is to find AB
it seems quite easy ,its just 6cm. I can solve it but when supposing that AB is a tangent (and this is not given in the problem) also i can't make use of the right angle opposite to the radius of this circle , so there must be something wrong with my answer.

so ,can u help?

Last edited by a moderator:

tiny-tim
Homework Helper
Hello Misr!
… I can solve it but when supposing that AB is a tangent (and this is not given in the problem) …

(hmm … not exactly to scale, is it? )

I'm sure AB is intended to be a tangent …

otherwise, B could be anywhere!

Yes I think so too
its just tangent

Thanks for help .