atlcharm

I do understand you can assume nothing from the diagrams. My question is on the principles. Here is the question which I've inserted in three photos part 1: https://docs.google.com/file/d/0B8G2c7VPiWjoSnJjUHRWQ0NoLTA/edit?usp=sharing part 2: https://docs.google.com/file/d/0B8G2c7VPiWjoUHpraDVkZVpRekE/edit?usp=sharing part 3: https://docs.google.com/file/d/0B8G2c7VPiWjoYkxsZXBHWFNRZUU/edit?usp=sharing My answer would have easily been C - that m and n are equal (the answer is D). I didn't assume that based on the pic. I assumed that because line AD and DC are equal. I thought that equal-sized lines had equal-sized angles. I'm getting this from all the rules on triangles and angles. For instance here: https://docs.google.com/file/d/0B8G2c7VPiWjoMWlkZVBpYkExOVU/edit?usp=sharing Can anyone help me get this straight in my head? I feel like a lot of this stuff is just memorization, but I'd like to make valid connections.