2. CHAPTER 2 : POLYGONS II
Names of Polygons
Name | Sides | Interior Angle | Exterior Angle |
Triangle (or Trigon) | 3 | 60° | 120° |
Quadrilateral (or Tetragon) | 4 | 90° | 90° |
5 | 108° | 72° | |
6 | 120° | 60° | |
Heptagon (or Septagon) | 7 | 128.571° | 51.429° |
Octagon | 8 | 135° | 45° |
Nonagon (or Enneagon) | 9 | 140° | 30° |
Decagon | 10 | 144° | 36° |
3. CHAPTER 3 : CIRCLES II
Definitions related to circles:
Arc: A continuous piece of a circle is called an arc. In other words, any portion of the circumference of a circle is called an arc.
Chord: A straight line joining any two points on the circumference of a circle is called a chord.
Circumference: The perimeter of a circle is called its circumference
Diameter: Any straight line drawn through the centre and terminating at both ways by the circumference is called a diameter.
Origin: Origin refers to the center of a circle
Pi (
): An approximate value of is 22/7 which is correct to two decimal places. A more accurate value of is 3.14159 which is correct to five decimal places. Radius: The constant distance of every point on the circle from its centre is called the radius of the circle. It is half of the diameter.
Sector: A sector is that part of a circle, which lies between an arc and two radii joining the extremities of the centre. The most important sector is a quadrant, which is one-fourth of the circle.
Tangent of a circle: It is a line perpendicular to the radius that touches only one point on the circle.
Circumference of a circle: = 2
r where is 22/7 or 3.14159
