MathDB
Area of an Obtuse Triangle

Source:

January 14, 2009
geometrytrigonometryratio

Problem Statement

Equilateral ABC \triangle ABC has side length 2 2, M M is the midpoint of AC \overline{AC}, and C C is the midpoint of BD \overline{BD}. What is the area of CDM \triangle CDM? [asy]size(200);defaultpen(linewidth(.8pt)+fontsize(8pt));
pair B = (0,0); pair A = 2*dir(60); pair C = (2,0); pair D = (4,0); pair M = midpoint(A--C);
label("AA",A,NW);label("BB",B,SW);label("CC",C, SE);label("MM",M,NE);label("DD",D,SE);
draw(A--B--C--cycle); draw(C--D--M--cycle);[/asy]<spanclass=latexbold>(A)</span> 22<spanclass=latexbold>(B)</span> 34<spanclass=latexbold>(C)</span> 32<spanclass=latexbold>(D)</span> 1<spanclass=latexbold>(E)</span> 2 <span class='latex-bold'>(A)</span>\ \frac {\sqrt {2}}{2}\qquad <span class='latex-bold'>(B)</span>\ \frac {3}{4}\qquad <span class='latex-bold'>(C)</span>\ \frac {\sqrt {3}}{2}\qquad <span class='latex-bold'>(D)</span>\ 1\qquad <span class='latex-bold'>(E)</span>\ \sqrt {2}