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Geometry Level 3

The beige shape pictured is comprised of 8 arcs of unit radius. A B = B C = 2 2 AB=BC=2\sqrt{2} and A B C = 13 5 \angle ABC=135^{\circ}

FInd the area of the shape.


The answer is 11.1415925.

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2 solutions

Jeremy Galvagni
Oct 24, 2018

The angle is a bit of a red herring. Changing it will not alter the area of the shape (unless it is too small.) Change it to 180 degrees and color as so:

We see the light blue segments can be moved to the light green to form four green squares each of area 2 2 = 2 \sqrt{2}^{2}=2 . The red segment on one end can move to the other side to complete a single circle of unit radius.

Total area: 8 + π 11.14159265 8+\pi \approx \boxed{11.14159265}

David Vreken
Oct 24, 2018

The shape can be subdivided into 3 3 sets of congruent shapes:

There are 16 16 pink shapes that are 1 8 \frac{1}{8} unit circles for an area of 16 1 8 π 1 2 = 2 π 16 \cdot \frac{1}{8} \pi \cdot 1^2 = 2 \pi .

There are 4 4 blue shapes that are the difference between a unit square and a 1 4 \frac{1}{4} unit circle for an area of 4 ( 1 1 4 π 1 2 ) = 4 π 4(1 - \frac{1}{4} \pi \cdot 1^2) = 4 - \pi .

There are 4 4 yellow shapes that are unit squares for an area of 4 1 2 = 4 4 \cdot 1^2 = 4 .

This gives a total area of 2 π + 4 π + 4 = 8 + π 11.1415925 2 \pi + 4 - \pi + 4 = 8 + \pi \approx \boxed{11.1415925} .

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