A large circle at the center, surrounded by smaller circles of different sizes and colors.
CBSE 10

CBSE 10 Geometry: The Secrets of the Perfect Symmetry of Circles (Formulas Revealed)

May 16, 2024

If you are studying geometry, then you must learn about circles. In this article, we will cover everything you need to know about circles, including definitions, formulas, and solved examples.

Definition

A circle is a closed shape that is perfectly round. It has no corners or edges. In geometry, a circle is defined as a set of points that are equidistant from a fixed point, called the center.

Circle shaped objects

Circles can be found in many objects in our daily life. A wheel, a clock, a pizza, and a frisbee are all examples of objects that are circular in shape.

How to draw a circle?

Drawing a circle is easy. All you need is a compass and a straight edge. Here are the steps to draw a circle:

  1. Place the compass on a piece of paper.
  2. Adjust the width of the compass to the desired size of the circle.
  3. Place the point of the compass on the paper and draw a circle.

Parts of circle

A circle has several parts, including the center, radius, diameter, chord, sector, and segment.

Center of circle (O)

The center of a circle is the fixed point that is equidistant from all points on the circle. It is denoted by the letter "O". The center is the point around which the rest of the circle is constructed, and it is often used as a reference point for other measurements, such as the radius and diameter.

Radius of circle (r)

The radius of a circle is the distance from the center of the circle to any point on the circle. It is denoted by the letter "r".

Diameter of circle (d)

The diameter of a circle is the distance across the circle, passing through the center. It is twice the length of the radius. It is denoted by the letter "d".

Chord of circle

A chord of a circle is a straight line segment that connects two points on the circle. The diameter of a circle is a special type of chord that passes through the center of the circle. The length of a chord can be calculated using the distance formula or the Pythagorean theorem.

Sector of circle

A sector of a circle is a region bounded by two radii of the circle and an arc of the circle. It is similar to a slice of pizza or a piece of pie. The two radii that bound the sector are called the initial radius and terminal radius, and the arc that bounds the sector is called the sector arc.

Sectors are often used in real-world applications, such as calculating the area of a slice of pizza or the angle of view of a camera lens.

Segment of circle

A segment of a circle is a region bounded by a chord and an arc of the circle. It is similar to a slice of pizza or a piece of pie, but it does not include the center of the circle. The chord that bounds the segment is called the base of the segment, and the arc that bounds the segment is called the segment arc.

Segments are often used in real-world applications, such as calculating the area of a pizza slice or the angle of view of a camera lens.

Formulas

Here are some important formulas related to circles:

  • Circumference of a Circle = 2πr or πd
  • Area of a Circle = πr²

Properties of circles

Here are some important properties of circles:

  • The diameter of a circle is twice the radius.
  • The circumference of a circle is the distance around the circle.
  • The area of a circle is the region enclosed by the circle.
  • The radius is perpendicular to the tangent at the point of contact.

Solved examples

Example 1:

Find the circumference of a circle with radius 5 cm.

✅  Solution: Circumference of the circle = 2πr = 2π * 5 = 10π cm.

Example 2:

Find the area of a circle with diameter 6 cm.

✅  Solution:
      1. Radius of the circle = 6 / 2 = 3 cm.
      2. Area of the circle = πr² = π * 3² = 9π cm².

Practice problems

  • Find the circumference of a circle with diameter 10 cm.
  • Find the area of a circle with radius 7 cm.

FAQs

What is called a circle?

A circle is a closed shape that is perfectly round. It has no corners or edges. In geometry, a circle is defined as a set of points that are equidistant from a fixed point, called the center.

What are the different parts of a circle?

A circle has several parts, including the center, radius, diameter, chord, sector, and segment.

Which formulas about circles do we have?

Here are some important formulas related to circles:

  • Circumference of a Circle = 2πr or πd
  • Area of a Circle = πr²

Conclusion

Circles are an important part of geometry, and understanding them is crucial for solving many mathematical problems. We hope this article has been helpful in teaching you everything you need to know about circles. If you need further assistance, visit Aha AI for more resources.

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