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"I am having some trouble proving a Triangle is Isosceles.  There is a picture of a triangle, with points A-D.  The top point is A, bottom Left is B, bottom right is C.  A line is in between (perpendicular) A and D.  Point D is the bottom middle of the triangle.  I need to have a statement and reason.
Attached is the pdf.

My question is that I need another statement/reason for angles.  What am I missing???
Thank You!!!"

I could work with your method, but this one is obvious to me.

Since the angles at B and C are equal and angles BDA and CDA are right triangles,
angle BAD and angle DAC are also both equal since the sum of angles in a triangle
is always 180.

Given the angles are always equal and both share the side DA,
this says that the other sides are equal.

That is, the line BC is cut in half and the line BA has the same length at line CA.
From here, it can be shown that thee two triamgles are relected on each other.
Once this has been done, anything else can be found.

Is this what the problem is suppose to prove?


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Scott A Wilson


I can answer whatever questions you ask except how to trisect an angle. The ones I can answer include constructing parallel lines, dividing a line into n sections, bisecting an angle, splitting an angle in half, and almost anything else that is done in geometry.


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