standard_description: For any number from 1 to 9, find the number that makes 10 when added to the given number, e.g., by using objects or drawings, and record the answer with a drawing or equation.
problem_activity: Task
Lisa makes an octagon by successively folding a square piece of paper as follows.  First, she folds the square in half vertically and horizontally and also along both diagonals leaving these creases:
[IMG]
Next, Lisa makes four more folds, identifying each pair of adjacent lines of symmetry for the square used for the folds in the first step:
[IMG]
Finally Lisa folds the four corners of her shape along the red creases marked below:
[IMG]
Explain why the shape Lisa has made is a regular octagon.


aligns: no