Question
The length of a side of an equilateral triangle is 18
cm. The area (in cm²) of the region lying between the circumcircle and the incircle of the triangle is [use use π =22/7]Solution
Side of the equilateral triangle = 18 cm Radius of circum - circle R = 18/√3 cm Radius of in - circle r = 18/2√3 = 9/√3 cm Area between the circum - circle and in – circle = π (R2 – r²) = π (R+ r) (R-r) = (22/7) × (18/√3 + 9/√3) (18/√3-9/√3) = (22/7) × 27/√3 × 9/√3 = (81×22)/7 = 1782/7 cm² =254(4/7) cm2
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