Editing Mathematical proof (section)

===Visual proof===
Although not a formal proof, a visual demonstration of a mathematical theorem is sometimes called a "[[proof without words]]". The left-hand picture below is an example of a historic visual proof of the [[Pythagorean theorem]] in the case of the (3,4,5) [[triangle]].
<gallery>
File:Chinese pythagoras.jpg|Visual proof for the (3,4,5) triangle as in the [[Zhoubi Suanjing]] 500–200&nbsp;BCE.
File:Pythagoras-2a.gif|Animated visual proof for the Pythagorean theorem by rearrangement.
File:Pythag anim.gif|A second animated proof of the Pythagorean theorem.
</gallery>

Some illusory visual proofs, such as the [[missing square puzzle]], can be constructed in a way which appear to prove a supposed mathematical fact but only do so by neglecting tiny errors (for example, supposedly straight lines which actually bend slightly) which are unnoticeable until the entire picture is closely examined, with lengths and angles precisely measured or calculated.