Newell's Nook features this colorful poster with the acronym MATH: Mistakes Allow Thinking to Happen. It is a tool for teachers who teach growth mindset in their classrooms and support students in seeing the power of mistakes in the learning process. It's a reminder that all mathematical thinking is valuable and can help us learn!
Teaching 5th grade the last 4 years, we went back and forth on that silly cone and cylinder too. How many edges do they really have? Glad to see someone else is just as confused as I. (By the way, it's all in the wording of your definition of edge.)
Sites that I can't do without as a math teacher (and what's so special about each one!) Links to virtual manipulatives, discovery-based lessons, free graphing software, question prompts, eBooks, and more.... Tons of resources for math teachers