Problem: Given square ABCDA B C DABCD with side 888 feet. A circle is drawn through vertices AAA and DDD and tangent to side BCB CBC. The radius of the circle, in feet, is:
Answer Choices:
A. 444
B. 424 \sqrt{2}42​
C. 555
D. 525 \sqrt{2}52​
E. 666 Solution:
r2=42+(8−r)2r^{2}=4^{2}+(8-r)^{2}r2=42+(8−r)2 \quad
16r=8016 r=8016r=80
r=5r=5r=5