Lines and angles - 4th may

A VERY GOOD MORNING BOYS!


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We will start a fresh topic today from GEOMETRY.

The Dictionary defines GEOMETRY as the branch of mathematics concerned with the properties and relations of points, lines, surfaces, solids, and higher dimensional analogues.

Today by the end of the blog, you will be able to:
(i) Define line, ray and line segment.
(ii) Relate the angles as COMPLEMENTARY, SUPPLEMENTARY and ADJACENT ANGLES.

IMPORTANT INSTRUCTION:
USE PENCIL AND RULER TO MAKE FIGURES.
USE COLORFUL PENS TO MAKE IMPORTANT POINTS OR HIGHLIGHT IMPORTANT NOTES.
NOTE DOWN THE TEXT IN BLUE IN YOUR NOTEBOOK.

LET US BEGIN......

Line:

A line is a straight figure which doesn’t have an endpoint and extends infinitely in opposite directions.

Ray:

A ray is a straight line, which starts from a fixed point and moves in one direction.

Line Segment

A portion of the line formed with two definite points is called a Line Segment. A line is a one-dimensional figure and has no thickness.

Angle

Two rays joined at a single point form an angle is formed. 

An Angle is a combination of two line segments at a common endpoint. 

The common point is called Vertex of the angle.
The two line segments are sides or arms of the angle formed.

Types of Angles

There are basically 6 types of angles which are:

1. Acute Angle: If an angle is less than 90 degrees, then it is called an Acute angle
2. Obtuse Angle: If an angle is more than 90 degrees, then it is called Obtuse Angle
3. Right Angle: If an angle is exactly at 90 degrees, then it is called Right Angle.
4. Straight Angle: If an angle is exactly 180 degrees, then it is called Straight Angle.
5. Reflex Angle: If the angle is more than 180 degree but less than 270 degrees, it is denoted as a Reflex angle.
6. Full Angle: A 360-degree angle is called a Full angle.

RELATED ANGLES:

Complementary PAIR OF  ANGLES : THE TWO ANGLES WHOSE SUM IS 90°

Supplementary Angle: THOSE TWO ANGLES  WHOSE SUM   is 180°

Adjacent Angle: Adjacent angles(1) have a common vertex and
                                                     (2)a common ARM
                                               (3) THE NON -COMMON ARMS ARE ON THE EITHER SIDE .

 CAN  ANGLE DBC AND ABC  be called     as adjacent angles ????? 

angle DBC IS A PART OF ANGLE ABC and not adjacent to it .

Let us now try to solve Exercise 5.1

Solve the other two parts yourself.

Solve the other two parts yourself.

Question 3:

For Question No. 4, watch the video.

https://www.youtube.com/watch?v=9iwtExWQaeg

Similarly,

Question 5:

To find two equal supplementary angles:

Let one of the supplementary angles be x.

x + x = 180°

-----------------Solve to find 'x'

Think about Question 7

I think you will be able to give the reasons.

 HOMEWORK: 

1. Complete the Exercise 5.1, Question 5 and 7 are HW. Complete the remaining parts of Question 1, 2 and 3.

THIS IS ALL FOR TODAY.

SEE YOU TOMORROW.