Geometry
Created by Akshay Madhira
Maths Teacher - Neeraja Ma'am
Class Teacher - Sudha Ma'am
Types of Angles
Different angles are formed when one arm of an angle is fixed and the other arm turns with the vertex.
Angle of 0° or zero angle
When the two arms of an angle coincide or overlap each other, such that the arms have not turned at all, then the angle is called the zero angle.
Complete angle
A complete turn is equal to an angle of 360°. It is called a complete angle. We can see that an angle of 360° can coincide with an angle of 0°.
Straight angle
An angle measuring 180° is called a straight angle. It looks like a straight line. It is one-half of a complete angle.
Right angle
An angle of 90° is called a right angle. It is one-fourth of a complete angle. If two lines interest each other making an angle of 90°, they are said to be perpendicular to each other.
Acute angle
An angle smaller than a right angle(90°)but more than a 0° angle is called an acute angle.
Obtuse angle
An angle smaller than a straight(180°)but greater than a right angle(90°) angle is called an obtuse angle.
Reflex angle
An angle whose measure is greater than 180° and less than 360° is called a reflex angle.
Circles
A circle is a closed curve in which every point on its boundary is at the same distance from a fixed point known as its centre
Radius
The radius of a circle is the distance from the centre of the circle to any point on the circle.
Diameter
The diameter of a circle is twice as long as the radius. It is a line segment joining two points on the boundary of the circle which passes through the centre.
Chord
A chord is a line segment joining any two points on the boundary of a circle.
Circumference
The length of the boundary of a circle is called its circumference.
Semicircle
Half of a circle is a semicircle. The arc representing the semicircle is called a semicircular arc.
Quadrant of a circle
One-fourth or one-quarter of a circle is a quadrant.
Measure the angle between the radii that form a quadrant. It is 90° or a right angle.
Symmetry
A plane shape is said to be symmetrical if we can draw a line through it in such a way that the part of the the shape on one side of the line is a reflection of the part on the other side. The line is known as a line of symmetry.
Symmetry
A plane shape is said to be symmetrical if we can draw a line through it in such a way that the part of the the shape on one side of the line is a reflection of the part on the other side. The line is known as a line of symmetry.