MathDB
Math Prize 2021 Problem 3

Source:

September 19, 2021
Math Prize for Girlsgeometry

Problem Statement

Let OO be the center of an equilateral triangle ABCABC of area 1/π1/\pi. As shown in the diagram below, a circle centered at OO meets the triangle at points DD, EE, FF, GG, HH, and II, which trisect each of the triangle's sides. Compute the total area of all six shaded regions. [asy] unitsize(90); pair A = dir(0); pair B = dir(120); pair C = dir(240); draw(A -- B -- C -- cycle); pair D = (2*A + B)/3; pair E = (A + 2*B)/3; pair F = (2*B + C)/3; pair G = (B + 2*C)/3; pair H = (2*C + A)/3; pair I = (C + 2*A)/3; draw(E -- F); draw(G -- H); draw(I -- D); draw(D -- G); draw(E -- H); draw(F -- I); pair O = (0, 0); real r = 1/sqrt(3); draw(circle(O, r)); fill(O -- D -- E -- cycle, gray); fill(O -- F -- G -- cycle, gray); fill(O -- H -- I -- cycle, gray); fill(arc(O, r, -30, 30) -- cycle, gray); fill(arc(0, r, 90, 150) -- cycle, gray); fill(arc(0, r, 210, 270) -- cycle, gray); label("AA", A, A); label("BB", B, B); label("CC", C, C); label("DD", D, unit(D)); label("EE", E, unit(E)); label("FF", F, unit(F)); label("GG", G, unit(G)); label("HH", H, unit(H)); label("II", I, unit(I)); label("OO", O, C); [/asy]