MathDB

18

Part of 1994 AMC 12/AHSME

Problems(1)

1994 AMC 12 #18

Source:

12/30/2011
Triangle ABCABC is inscribed in a circle, and ∠B=∠C=4∠A\angle B = \angle C = 4\angle A. If BB and CC are adjacent vertices of a regular polygon of nn sides inscribed in this circle, then n=n= [asy] draw(Circle((0,0), 5)); draw((0,5)--(3,-4)--(-3,-4)--cycle); label("A", (0,5), N); label("B", (-3,-4), SW); label("C", (3,-4), SE); dot((0,5)); dot((3,-4)); dot((-3,-4)); [/asy] <spanclass=′latex−bold′>(A)</span> 5<spanclass=′latex−bold′>(B)</span> 7<spanclass=′latex−bold′>(C)</span> 9<spanclass=′latex−bold′>(D)</span> 15<spanclass=′latex−bold′>(E)</span> 18 <span class='latex-bold'>(A)</span>\ 5 \qquad<span class='latex-bold'>(B)</span>\ 7 \qquad<span class='latex-bold'>(C)</span>\ 9 \qquad<span class='latex-bold'>(D)</span>\ 15 \qquad<span class='latex-bold'>(E)</span>\ 18
AMC