Moon Math
Geometry
Level
3
Make a circle with OA as the radius, extend OA to find a point C, use CA as the radius to make an arc intersect with E and F, and then use CA as the diagonal for square ABCD. If E, O, and F are collinear, AB=10, find the yellow part area =?
5
50
10
100
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1 solution
Connect EF, AE, AF, you can get OE=OF=OA, AE=AF=√2OA, then
=
⇒
=
and
=
request=100