MathDB
Rectangle to pyramid

Source:

March 21, 2006
geometryrectangle3D geometrypyramidcircumcirclespheretetrahedron

Problem Statement

The rectangle ABCDABCD below has dimensions AB=123AB = 12 \sqrt{3} and BC=133BC = 13 \sqrt{3}. Diagonals AC\overline{AC} and BD\overline{BD} intersect at PP. If triangle ABPABP is cut out and removed, edges AP\overline{AP} and BP\overline{BP} are joined, and the figure is then creased along segments CP\overline{CP} and DP\overline{DP}, we obtain a triangular pyramid, all four of whose faces are isosceles triangles. Find the volume of this pyramid.
[asy] pair D=origin, A=(13,0), B=(13,12), C=(0,12), P=(6.5, 6); draw(B--C--P--D--C^^D--A); filldraw(A--P--B--cycle, gray, black); label("AA", A, SE); label("BB", B, NE); label("CC", C, NW); label("DD", D, SW); label("PP", P, N); label("13313\sqrt{3}", A--D, S); label("12312\sqrt{3}", A--B, E);[/asy]