chapter 3 lines and angles class 7
Answers
Introduction to Lines and Angles
- Related angles
- Complementary Angles
- Supplementary Angles
- Adjacent Angles
- Linear Pair
- Vertically Opposite Angles
- Pairs of Lines
- Intersecting Lines
- Transversal
- Angles made by a Transversal
- Transversal of Parallel Lines
- Checking for Parallel Lines
Angles:
In plane geometry, an angle is the figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle. Angles formed by two rays lie in a plane, but this plane does not have to be a Euclidean plane.
Line:
In geometry, the notion of line or straight line was introduced by ancient mathematicians to represent straight objects with negligible width and depth. Lines are an idealization of such objects, which are often described in terms of two points or referred to using a single letter.
Point:
In modern mathematics, a point refers usually to an element of some set called a space. More specifically, in Euclidean geometry, a point is a primitive notion upon which the geometry is built, meaning that a point cannot be defined in terms of previously defined objects.
Ray:
In geometry, a ray can be defined as a part of a line that has a fixed starting point but no end point. It can extend infinitely in one direction. On its way to infinity, a ray may pass through more than one point. ... The vertex of the angles is the starting point of the rays.
Line segment:
In geometry, a line segment is a part of a line that is bounded by two distinct end points, and contains every point on the line between its endpoints. A closed line segment includes both endpoints, while an open line segment excludes both endpoints; a half-open line segment includes exactly one of the endpoints.
Acute angle: The angle that is between 0° and 90° is an acute angle, ∠A in the figure below.
acute angle
Obtuse angle: The angle that is between 90° and 180° is an obtuse angle, ∠B as shown below.
obtuse angle
Right angle: The angle that is 90° is a Right angle, ∠C as shown below.
right angle
Straight angle: The angle that is 180° is a straight angle, ∠AOB in the figure below.
reflex angle: A reflex angle is an angle of more than . A full angle is therefore a reflex angle, while acute, obtuse, right, and straight angles are not.
Complete Angle: An angle whose measure is equal to 360° is called a complete angle.
Zero Angle: Angle measuring zero 0°