Editing Mathematical proof (section)

===Two-column proof===
[[File:twocolumnproof.png|thumb|right|A two-column proof published in 1913]]

A particular way of organising a proof using two parallel columns is often used as a [[mathematical exercise]] in elementary geometry classes in the United States.<ref>{{cite journal |first=Patricio G. |last=Herbst |title=Establishing a Custom of Proving in American School Geometry: Evolution of the Two-Column Proof in the Early Twentieth Century |journal=[[Educational Studies in Mathematics]] |volume=49 |issue=3 |year=2002 |pages=283–312 |doi=10.1023/A:1020264906740 |hdl=2027.42/42653 |s2cid=23084607 |url=https://deepblue.lib.umich.edu/bitstream/2027.42/42653/1/10649_2004_Article_5096042.pdf |hdl-access=free }}</ref> The proof is written as a series of lines in two columns. In each line, the left-hand column contains a proposition, while the right-hand column contains a brief explanation of how the corresponding proposition in the left-hand column is either an axiom, a hypothesis, or can be logically derived from previous propositions. The left-hand column is typically headed "Statements" and the right-hand column is typically headed "Reasons".<ref>{{cite web|url=https://www.onemathematicalcat.org/Math/Geometry_obj/two_column_proof.htm |title=Introduction to the Two-Column Proof |author=Dr. Fisher Burns |website=onemathematicalcat.org |access-date=October 15, 2009}}</ref>