1. The problem statement, all variables and given/known data If you take an 8.5in by 11in piece of paper and fold one corner over so it just touches the opposite edge as seen in figure (http://wearpete.com/myprob.jpg [Broken]). Find the value of x that makes the area of the right triangle A a maximum? 2. Relevant equations A = 1/2(xy) x2+y2=(8.5-y)2 3. The attempt at a solution x2+y2=(8.5-y)2 x = sqrt((8.5-y)2-y2) A = 1/2(y)(sqrt((8.5-y)2-y2)) da/dx = ((y2-4.25y)/sqrt((8.5-y)2-y2))+1/2(sqrt(-17y-72.25)) I know that at da/dx=0 the triangle is maximized but da/dx is undefined at y=0 (y graphically). I am pretty sure my derivative is right but maybe I missed something there. Thanks for taking a look.