Difference between revisions of "University of South Carolina High School Math Contest/1993 Exam/Problem 3"

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== Problem ==
 
== Problem ==
 
If 3 circles of radius 1 are mutually tangent as shown, what is the area of the gap they enclose?
 
If 3 circles of radius 1 are mutually tangent as shown, what is the area of the gap they enclose?
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<center>[[Image:Usc93.3.PNG]]</center>
  
 
<center><math> \mathrm{(A) \ }\sqrt{3}-\frac{\pi}2 \qquad \mathrm{(B) \ } \frac 16 \qquad \mathrm{(C) \ }\frac 13 \qquad \mathrm{(D) \ } \frac{\sqrt{3}}2 - \frac{\pi}6 \qquad \mathrm{(E) \ } \frac{\pi}6 </math></center>
 
<center><math> \mathrm{(A) \ }\sqrt{3}-\frac{\pi}2 \qquad \mathrm{(B) \ } \frac 16 \qquad \mathrm{(C) \ }\frac 13 \qquad \mathrm{(D) \ } \frac{\sqrt{3}}2 - \frac{\pi}6 \qquad \mathrm{(E) \ } \frac{\pi}6 </math></center>

Revision as of 13:13, 23 July 2006

Problem

If 3 circles of radius 1 are mutually tangent as shown, what is the area of the gap they enclose?

Usc93.3.PNG
$\mathrm{(A) \ }\sqrt{3}-\frac{\pi}2 \qquad \mathrm{(B) \ } \frac 16 \qquad \mathrm{(C) \ }\frac 13 \qquad \mathrm{(D) \ } \frac{\sqrt{3}}2 - \frac{\pi}6 \qquad \mathrm{(E) \ } \frac{\pi}6$

Solution

Construct an equilateral triangle whose sidelengths (length $2$) are composed of the radii fo the circles. The area is thus $\sqrt{3}-\pi/2$.