matter on topic lines and angles class 7 for project
Answers
Lines And Angles
(a) Segment:- - A part of line with two end points is called a line-segment.
A line segment is denoted by AB and its length is is denoted by AB.
(b) Ray:- - A part of a line with one end-point is called a ray.
We can denote a line-segment AB, a ray AB and length AB and line AB by the same symbol AB.
(c) Collinear points: - If three or more points lie on the same line, then they are called collinear points, otherwise they are called non-collinear points.
(d) Angle:- - An angle is formed by two rays originating from the same end point.
The rays making an angle are called the arms of the angle and the end-points are called the vertex of the angle.
(d) Types of Angles:-
(i) Acute angle: - An angle whose measure lies between 0° and 90°, is called an acute angle.
(ii) Right angle: - An angle, whose measure is equal to 90°, is called a right angle.
(iii) Obtuse angle: - An angle, whose measure lies between 90° and 180°, is called an obtuse angle.
(iv) Straight angle: - The measure of a straight angle is 180°.
(v) Reflex angle: - An angle which is greater than 180° and less than 360°, is called the reflex angle.
(vi) Complimentary angle: - Two angles, whose sum is 90°, are called complimentary angle.
(vii) Supplementary angle: - Two angles whose sum is 180º, are called supplementary angle.
(viii) Adjacent angle: - Two angles are adjacent, if they have a common vertex, common arm and their non-common arms are on different sides of the common arm.