# Common Notion 4

- Author:
- Mathew Purser

Things which coincide with one another equal one another.

**If two things can be moved directly onto each other and completely overlap (superposition), then they are equal.**## Tool Practice

Using the applet below, convince yourself that the two triangles are the same by CN4.
HINT: Drag the orange triangle onto the black triangle and see if all the points match up