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Circle geometry also calculates symmetries of a circle, congruence and similarity of circle, angles at the centre and circumference and in a semicircle, cyclic quadrilateral and trigonometry. The circle geometry is a very useful tool.

Given: radius r = 20 cm.

The Formula for area of circle is area = π r * r = π r

3.14 x 20 x 20 = 3.14 x 400 =

Circumference of a circle = 2 π r

2 π x 20 = 2 x 3.14 x 20 =

arc if central angle is 30 degrees.

Central angle θ = 30 degrees

Area of sector = (θ/360) π r

(30/360) x 3.14 x 30 x 30 = 1/120 x 3.14 x 900 =

Length of circular arc = θ x (π/180) x r

30 x (3.14/180) x 30 = 5 x 3.14 =