Areas Related To Circles

The area of an equilateral triangle ABC is 17320.5 cm2. With each vertex of the triangle as centre, a circle is drawn with radius equal to half the length of the side of the triangle (see Fig. 12.28). Find the area of the shaded region. (Use π = 3.14 and √3 = 1.73205)

Solution: An equilateral triangle is ABC. As a result, ∠ A = ∠ B = ∠ C = 60° There are three sectors, each of which makes a 60°. The area of ΔABC = 17320.5 cm2 ⇒ √3/4 ×(side)2 = 17320.5 ⇒...

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Fig. 12.3 depicts an archery target marked with its five scoring regions from the centre outwards as Gold, Red, Blue, Black and White. The diameter of the region representing Gold score is 21 cm and each of the other bands is 10.5 cm wide. Find the area of each of the five scoring regions.

Solution: r1 = 21/2 cm is the radius of the first circle (as diameter D is given as 21 cm) As a result, the area of the gold region = π r12 = π(10.5)2 = 346.5 cm2. Given that each of the...

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