MathDB
Very nice geometry and probability combination

Source:

December 4, 2005
geometryprobabilitytrapezoidrectangle

Problem Statement

A point P P is selected at random from the interior of the pentagon with vertices A \equal{} (0,2), B \equal{} (4,0), C \equal{} (2 \pi \plus{} 1, 0), D \equal{} (2 \pi \plus{} 1,4), and E \equal{} (0,4). What is the probability that APB \angle APB is obtuse? [asy] size(150); pair A, B, C, D, E; A = (0,1.5); B = (3,0); C = (2 *pi + 1, 0); D = (2 * pi + 1,4); E = (0,4); draw(A--B--C--D--E--cycle); label("AA", A, dir(180)); label("BB", B, dir(270)); label("CC", C, dir(0)); label("DD", D, dir(0)); label("EE", E, dir(180)); [/asy] <spanclass=latexbold>(A)</span> 15<spanclass=latexbold>(B)</span> 14<spanclass=latexbold>(C)</span> 516<spanclass=latexbold>(D)</span> 38<spanclass=latexbold>(E)</span> 12 \displaystyle <span class='latex-bold'>(A)</span> \ \frac {1}{5} \qquad <span class='latex-bold'>(B)</span> \ \frac {1}{4} \qquad <span class='latex-bold'>(C)</span> \ \frac {5}{16} \qquad <span class='latex-bold'>(D)</span> \ \frac {3}{8} \qquad <span class='latex-bold'>(E)</span> \ \frac {1}{2}