Shapes Rectangle Square Circle Triangle Rhombus Squircle Oval Hexagon Pentagon Trapezoid Kite Parallelogram Quadrilateral Polygon Nonagon Heptagon Decagon Octagon Ellipse Parallelepiped Tetrahedron Cylinder Prism Sphere Pyramid Frustum Polyhedron Dodecagon Dodecahedron Octahedron Torus Cube Cone Hyperbola Rectangular Prism Fibonacci Sequence Golden Ratio Parabola Rectangular Prism Fibonacci Sequence Calculators Fraction Calculator Mixed Fraction Calculator Greatest Common Factor Calulator Decimal to Fraction Calculator Fraction Calculator Mixed Fraction Calculator Greatest Common Factor Calulator Decimal to Fraction Calculator Arithmetic Whole Numbers Rational Numbers Place Value Irrational Numbers Natural Numbers Binary Operation Numerator and Denominator Decimal Order of Operations (PEMDAS) Scientific Notation Symmetry Fractions Triangular Number Complex Number Binary Number System Logarithm Binomial Theorem Quartic Function Mathematical Induction Group Theory Modular Arithmetic Euler’s Number Inequalities Sets De Morgan’s Laws Transcendental Numbers Rational Numbers Irrational Numbers Natural Numbers Binary Operation Numerator and Denominator Order of Operations (PEMDAS) Scientific Notation Triangular Number Binary Number System Binomial Theorem Quartic Function Mathematical Induction Modular Arithmetic De Morgan’s Laws Transcendental Numbers Table of Contents Last modified on August 3rd, 2023 chapter outline A closed, round geometric figure in which the set of all the points in the plane is equidistant from a given point called ‘center’. Parts and Properties 1) Radius – The line that joins the center of the circle to the outer boundary. It is usually represented by ‘ r ’ or ‘ R ’. The plural of radius is called radii. 2) Diameter – The line segment whose endpoints lie on the circle and that passes through the center. Its length is twice the length of a radius. It is represented by as -‘ d ’ or ‘ D ’. So, r = d /2 or R = D /2 3) Chord – The line segment whose endpoints lie on the circle, thus dividing a circle into two regions. The diameter is the longest chord of a circle. 4) Secant – An extended chord that cuts the circle at two distinct points. 5) Arc – The connected section of the circumference of a circle. 6) Tangent – A line that touches the circumference of a circle at a point. 7) Sector – A region bounded by two radii of equal length with a common center. 8) Segment – The segment of a circle is the region bounded by a chord and the arc subtended by the chord. Also known as the perimeter, it is the total distance covered around the circle. The formula is given below: Circumference ( C ) = 2πr , here r = radius, and π = 3.141 = 22/7 Problem: Finding the circumference of a circle when only the DIAMETER is known The diameter of a circle is 6 centimeters. Find the circumference As we know, C = 2πr , here r = d /2 = 6/2 cm = 3 cm Hence, C = 2 x 3.14 × 3 = 18.84 cm Problem: Finding the circumference of a circle when only the RADIUS is known

The radius of a circle is 4 inches. Find the circumference As we know, C = 2πr , here r = 4 inches = 2 × 3.14 × 4 = 25.12 inches It is the total space enclosed inside the boundary of the circle. It is also known as the ‘surface area of the circle’. The formula is given below: Area ( A ) = πr 2 , here r = radius, and π = 3.141 = 22/7 Problem: Finding the area of a circle when only the RADIUS is known Find the area of a circle with a radius of 9 cm As we know, A = πr 2 , here r = 9 cm = 3.14 × 9 × 9 = 254.34 cm 2 Problem: Finding the area of a circle when only the DIAMETER is known Find the area of a circle with a diameter of 10 cm As we know, A = πr 2 and r = d /2 = 10/2 = 5 cm = 3.14 × 5 × 5 = 78.5 cm 2 More Resources Area of a Circle Circumference of a Circle Equation of a Circle Diameter of a Circle Radius of a Circle Concentric Circles Semi circle Chord of a Circle Tangent of a Circle Arc of a Circle Secant of a Circle Sector of a Circle Center of a Circle Segment of a Circle Inscribed and Circumscribed Circles Quadrant of a Circle Congruent Circles Unit Circle Parametric Equation of Circle Area of a Circle Circumference of a Circle Equation of a Circle Diameter of a Circle Radius of a Circle Concentric Circles Chord of a Circle Tangent of a Circle Arc of a Circle Secant of a Circle Sector of a Circle Center of a Circle Segment of a Circle Inscribed and Circumscribed Circles Quadrant of a Circle Congruent Circles Parametric Equation of Circle Last modified on August 3rd, 2023 5 thoughts on “ Circle ” very good Reply Very good and satisfactory Reply Very good and satisfactory It’s very helpful for students all over the world and also the teachers Reply It’s very helpful for students all over the world and also the teachers it is very fantastic and very understandable Reply it is very fantastic and very understandable really good resource. Thank you. Reply really good resource. Thank you. Leave a comment Cancel reply Related Materials Circle Worksheets Parts of a Circle Worksheets Related Materials Join Our Newsletter © 2026 Mathmonks.com . All rights reserved. Reproduction in whole or in part without permission is prohibited.