Outside Fun

Geometry Level 5

The three blue circles with centers X , Y X, Y and Z Z are each tangent to two of the lines making up the triangle A B C ABC and each of them has twice the area of the incircle of the triangle A B C ABC . If the area of the triangle A B C ABC is 1, find the area of the triangle X Y Z XYZ and express it as a + b c a+b\sqrt{c} , where a , b a,b and c c are positive integers with c 1 c \neq 1 square-free. Submit your answer as a + b + c a+b+c .


The answer is 7.

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3 solutions

Marta Reece
May 18, 2016

Triangles ABC and XYZ are similar, since the sides of XYZ are parallel to sides of ABC, only distance R R (radius of blue circle) over. The ratio of R / r R/r is 2 \sqrt{2} , from the fact that areas of blue circles are twice the area of the incircle. Therefore the distance CZ is also 2 \sqrt{2} times the distance OC, where O is the center of the incircle. That makes the distance OZ, along with every other dimension in triangle XYZ, 1 + 2 1+\sqrt{2} times the corresponding distances, OC in this case, in triangle ABC. The ratio of the areas is proportional to the square of this figure, that is 3 + 2 2 3+2\sqrt{2} .

Mark C
May 29, 2016

AC is parallel to XY - not XZ. BA is parallel to ZX - not YZ.

Bob Kadylo - 5 years ago

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Thank you. I am correcting.

Niranjan Khanderia - 5 years ago

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