All of the triangles in the diagram are equilateral and share a center with all the circles. All of the internal circles and triangles are inscribed in the appropriate triangles and circles, respectively.
If the green area is equal to the red area, is the purple area equal to the yellow area?
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To go from the green circle to the purple circle takes two operations:
inscribe an equilateral triangle in the circle
inscribe a circle in the equilateral triangle
Going from red triangle to yellow triangle takes also two operations:
inscribe a circle in the equilateral triangle
inscribe an equilateral triangle in the circle
They are the same two operations and the order in which they are executed does not change the amount of shrinkage accomplished.
So the answer is: YES, the areas are equal.
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Details
If the green circle has radius R , the side of the orange triangle is a = 2 × R × cos 3 0 ∘ = 2 R 2 3 = R 3
The radius of the purple circle is then r = 2 a cos 3 0 ∘ 1 = 2 3 a = 2 3 R 3 = 2 R
If the side of the red triangle is A , then the radius of the blue circle is r = 2 A cos 3 0 ∘ 1 = 2 3 A
And the side of the yellow triangle a is a = 2 × r × cos 3 0 ∘ = 2 r 2 3 = r 3 = 2 3 A 3 = 2 A
Both dimensions are half of what they were, so they are in the same proportion and the areas remain equal to each other.
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Interestingly enough, the blue area is NOT equal the orange area.
To show this, we need the actual ratio between radius of the green circle R and side of the red triangle A . Their areas are equal, therefore:
π R 2 = 4 3 A 2
R A = 4 3 2 π ≈ 2 . 6 9
Orange triangle inscribed into the green circle has a side a = R 3
Blue circle inscribed into the red triangle has a radius r = 2 3 A
So the ratio r a = R 3 × A 2 3 = A 6 R = π 3 4 5 ≈ 2 . 2 3 = 2 . 6 9 ≈ R A