Introduction
In this section, we will be going further into geometry basics regarding lines and angles.
As we have already studied in the sixth grade, that every-day objects that we observe, can be simplified into shapes being formed by lines, curves and rays etc. and when bunched together they give rise to angles, polygons and so on.
We know that, a line segment has
If we extend the two end points in either direction endlessly, we get a
Thus, we can say that a
On the other hand, recall that a
In geometric terms, a house is made up of a bunch of lines- intersecting and parallel and the adjacent ones subsequently, make angles with each other.
Look at the images below. Can you visualise them to a basic layout which consists of only lines, line segments and angles?
Crystal Stones
Table
Alphabets made using matchsticks
Give some examples of line segments and rays from your daily life and discuss them with your friends.
The above figure (i) shows a line segment, (ii) shows a line and (iii) is a ray. A line segment AB is generally denoted by the symbol AB, a line CD is denoted by the symbol CD↔ and the ray PQ is denoted by PQ→.
Recall that an
In the first figure, line segments AB and BC intersect at B to form angle ∠ABC, and line segments BC and AC intersect at C to form angle ∠ACB and so on.
Whereas, in the second figure, lines PQ and RS intersect at O to form four angles ∠POS, ∠SOQ, ∠QOR and ∠ROP. An angle ABC is represented by the symbol ∠ABC.
We have already studied how to classify the angles as acute, obtuse or right angle.
Refer to the above two figure and observe the angles. Drag and drop the angles into the correct classification.
Note: While referring to the measure of an angle ABC, we shall write m∠ABC as simply ∠ABC. The context will make it clear, whether we are referring to the angle or its measure.
1. List ten figures around you and identify the acute, obtuse and right angles found in them
Solution: