more help with proof

I am sorry if I am doing this wrong by posting a new topic, but I am new to this and was not sure if I should add to my old post or start a new one. :? Anyway... here is my problem: Prove that tangents to a circle at the endpoints of a diameter are parallel. State what is given, what is to be proved, and your plan for proof. Then write a two-column proof. It will help you to draw a diagram with the points labeled. Here is what I have so far: I drew circle labeled circle a, drawing diameter through it. (putting A as the center of the diameter) Then I drew my tangents at the endpoints and labeled them BC and DE.

Given- BC and DE are tangent to circle A at the endpoints of the diameter.
Prove-BC is parallel to DE
Plan: (here is where i get very confused!) BD id diameter of circle A. Diameter is semicircle =180 degrees, therefore BA=90 and AD=90. BC and DE are equidistant from midpoint A on circle A therefore they are parallel.

statement reason
1. BD is diameter of circle A given
2. A is midpoint of BD def of midpoint
3. BA=AD midpoint thm Thm 2-1
4. BC is equidistant from DE therefore
they are parallel

I know that this is probably wrong. I am horrible with proofs. Please help!
Also, I am sorry it took so long to get back to this post. Thanks in advance for any help!!!!! Kelly[/list][/list][/code]

wrote two column wrong

I typed my two-colum proof in a confusing way so am retyping it
statement../..reason

1. BD is diameter of circle A../.. given
2. A is the midpoint of BD../.. def of midpoint
3.BA=AD../.. midpoint therom Thm. 2-1
4. BC is equidistant from DE, therefore BC is parallel to DE../.. ?????

I'm not exactly sure what tools you have to apply to this problem. I'll just throw out a couple of things and see if they mean anything to you.

1) A tangent is perpendicular to a radius at the point of tangency
2) In a plane, lines perpendicular to the same line are parallel.

Thanks, that helps alot.

You did a remarkable job of presenting the problem, for a first timer. Here are a few hints.
You have learned how to add to a previous post. If it hasn't been answered you can click on "edit" at the top and make any changes you want. (you can do that at any time but if it has an answer it is better to post your changes as a reply. It can get confusing if the answer doesn't apply to the edited post.)
It isn't a good idea to post a reply to an unanswered post. I usuallly look first at unanswereds and if you "answer" it, I could skip it.
For a two column proof you might look at clicking twice on the Code button then typing between the boxes. You can then keep things in columns. Looks better.
------------------
Gene