Question 1041084
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1. Wrong.  There is absolutely nothing other than your intuition that tells you angle ABC is a right angle. Yes, indeed, it looks like a right angle, but it might very well be an 89.999 degree angle and you would not be able to tell the difference and yet that would make your statement that BD is a bisector of angle ABC a completely false assertion.


2. Wrong.  Same reason.


3. Wrong.  "Knowing the bisector (1)" is meaningless (where did you meet it? at a cocktail party?), B is not the midpoint of anything, except perhaps an extended segment from A, C, or D through B to a point equidistant, and that would have absolutely nothing to do with proving that BD is a bisector of ABC.  You would have to know that the measure of angle ABD is 45 degrees or that the measure of angle ABC is 90 degrees or that angle ABC is a right angle.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  

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