No spoilers here

So I just finished reading The Curious Case of the Dog in the Nightime. Maybe it's because I'm dumb and I can't understand any math besides basic algebra, but I hated the end of the book.  "I got a puppy, I basically ignore my dad, now here's 4 pages of explaining my favorite math problem". The puppy part was cute, I liked the fact that  the story started with a dog and ended with a new dog.  However, I don't quite understand the significance  of have a four page explanation of a math problem as the end of a book. I understand that Christopher loved math, but why end with  an explanation of a math problem? Why not stop at, well, the end, just cut out the appendix (which is the 4 page explanation of Christopher's favorite math problem). Unless, to a trained, "math-savy" brain, the problem makes sence and the answer has some sort of significance and is a symbolic representation of the story. I read the last paragraph of the appendix and it made the answer sound like maybe the two sides of the triangle could represent his parents and the other side was him, because he could not be represented in the proper form. I'm not quite sure because I am awful at math, but if I had to take an educated guess at  why the end of the book was the way it was, I guess that would be why. Who would have known math could have symbolism.