"Why do we need to learn this?"
Pixar and Khan academy have teamed up to present an entire set of modules entitled "Pixar in a Box." The goal of the lessons are to allow the user to see how math can be used for creative purposes at Pixar for their animation technology. Hopefully, along the way, students will be inspired and see math in their everyday lives and see a purpose for what they are learning in school. Some of the modules even introduce a bit of coding to teach students how to build the characters.
Here's a short video clip introducing Pixar in a Box:
The modules start with a basic level for lesson one that elementary students can even tackle. The level two lessons progress into more depth and typically range from middle to high school level content. Here's a snapshot of the topics and grade ranges: