Hi Kreyn,
Three equal circles with radius r are drawn as shown, each with its centre on the circumference of the other two circles. A, B and C are the centres of the three circles. Prove that an expression for the area of the shaded region is:
\(A=\frac{r^2}{2}\left(\pi -\sqrt{3}\right)\)
Now AB, AC and BC are all radii, so they are all equal, so ABC is an equilateral triangles and all the angles are 60 degrees.
\(\boxed{\text{Area of triangle ABC=}\frac{1}{2}absinC }\\ \\~\\ Area\;\;ABC=\frac{1}{2}r^2sin60^\circ\\ Area\;\;ABC=\frac{1}{2}r^2*\frac{\sqrt3}{2}=\frac{\sqrt3\;r^2}{4}\)
Now I want to know what the area of minor segment AB is on the circle centred at C
\(Segment\; area = \frac{60}{360}\pi r^2\;-\;\frac{\sqrt3\;r^2}{4}\\ Segment\; area = \frac{2}{12}\pi r^2\;-\;\frac{3\sqrt3\;r^2}{12}\\ Segment\; area = \frac{2\pi r^2-3\sqrt3\;r^2}{12}\\ so\\ Shaded \;area = 3* \frac{2\pi r^2-3\sqrt3\;r^2}{12} + \;\frac{\sqrt3\;r^2}{4}\\ Shaded\; area = \frac{2\pi r^2-3\sqrt3\;r^2+\sqrt3\;r^2}{4} \\ Shaded\; area = \frac{2\pi r^2-2\sqrt3\;r^2}{4} \\ Shaded\; area = \frac{\pi r^2-\sqrt3\;r^2}{2} \\ Shaded\; area = \frac{ r^2}{2}(\pi -\sqrt3\;) \\\)
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