txags911 on 01 June 2007
Actually, even the way they are drawn, they could be slightly off and not congruent. Let's say you take one of the two angles that look like they are 90 degrees and bend them by 1 degree (or even less). As a result, what appears to be two lines intersecting in the middle will not actually be that. The lines will skew ever so slightly in the center. So one of the lines crossing will not be completely straight. So you've changed angles, left the two congruent sides as being congruent as the picture says, and even maintained the overall look of the picture. The changes are so small they would be barely noticeable. But the triangles are not congruent since one has a 90 degree angle on in and the other has an 89 degree one.
