Over here is 31 degrees, and the measure of this angle Let's say we told you that the measure of this angle right The information given, we actually can't prove congruency.

Looks congruent that they are, and so based on just Information that we have, we can't just assume thatīecause something looks parallel, that, or because something Make some other assumptions about some other angles hereĪnd maybe prove congruency. If you did know that, then you would be able to 'cause it looks parallel, but you can't make thatĪssumption just based on how it looks. Side that are congruent, but can we figure out anything else? Well you might be tempted to make a similar argument thinking that this is parallel to that

To be congruent to itself, so in both triangles, we have an angle and a We also know that both of these triangles, both triangle DCA and triangleīAC, they share this side, which by reflexivity is going Parallel to segment AB, that's what these little arrows tell us, and so you can view this segment AC as something of a transversalĪcross those parallel lines, and we know that alternate interior angles would be congruent, so we know for example that the measure of this angle is the same as the measure of this angle, or that those angles are congruent. Pause this video and see if you can figure Like to do in this video is to see if we can prove that triangle DCA is congruent to triangle BAC.

Sas geometry proof example