MathDB
Trig Graph Area

Source: AMC 12 2006B, Problem 24

February 17, 2006
trigonometrygeometryanalytic geometry3D geometryprobabilityquadraticsinequalities

Problem Statement

Let S S be the set of all points (x,y) (x,y) in the coordinate plane such that 0xπ2 0\le x\le \frac \pi2 and 0yπ2 0\le y\le \frac \pi2. What is the area of the subset of S S for which \sin^2 x \minus{} \sin x\sin y \plus{} \sin^2 y\le \frac 34? <spanclass=latexbold>(A)</span>π29<spanclass=latexbold>(B)</span>π28<spanclass=latexbold>(C)</span>π26<spanclass=latexbold>(D)</span>3π216<spanclass=latexbold>(E)</span>2π29 <span class='latex-bold'>(A) </span> \frac {\pi^2}9 \qquad <span class='latex-bold'>(B) </span> \frac {\pi^2}8 \qquad <span class='latex-bold'>(C) </span> \frac {\pi^2}6\qquad <span class='latex-bold'>(D) </span> \frac {3\pi^2}{16} \qquad <span class='latex-bold'>(E) </span> \frac {2\pi^2}9