Problem: The radius of the smallest circle containing the symmetric figure composed of the 3 unit squares shown at the right is
Answer Choices:
A. 2​
B. 1.25​
C. 1.25
D. 16517​​
E. None of these
Solution:
Let P be the center of the circumscribing circle. (See figure). We must Let P be the center of the circumscribing circle. (See figure). We must have AP2=PB2 so that (1−OP)2+12=(1+OP)2+(21​)2 and −2OP+1=2OP+41​, OP=161​. Hence AP2=(1−OP)2+12=(1613​)2+1=256169+256​=256425​=25625(17)​ and A P=\frac{5 \sqrt{17}}
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