The area of a rectangle is equal to the product of its base and altitude. Given R a rectangle with base b and altitude a. To prove R = a X b. Proof. Let U be the unit of surface. .R axb U' Then 1x1 But  is the area of R. A Treatise on Mensuration, Both in Theory and Practice  Page 91 by Charles Hutton  1788  703 pages Full view 
