Hello!!Hello!!Maths lovers Maths lovers

Our lesson today in..…

Geometry

Firstly.…What’s the deference between,

Excellent,Excellent,As you noticed!!As you noticed!!

We called them..

Line segment,

Straight lineAnd Ray

DefinitionsDefinitions::A line segment:

A set of points…..consisting of 2 distinct points like A and B (when we join them by a ruler)

AB¯=BA ¯

We can`t draw more than 1 line segment joining 2 points

It has 2 ends points ≈ It has length

A B

DefinitionsDefinitions::A straight line: Has an infinite ∞ number of points on it .

The 2 arrows show that it can be extended without limit on its 2 sides

AB¯=BA ¯

We can`t draw more than 1 straight line joining 2 points.

It has no starting point and no ending point so…we cant measure its length.

A B

DefinitionsDefinitions::A Ray:

The line segment AB¯ and all the points on the right side of the point B is a ray.

The arrow show that it can be extended without limit on its 1 sides.

AB¯ differs from BA ¯

It has a starting point and no ending point so…we cant measure its length.

A B

Straight linerayLine segment

AB is a subset of AB andAB is a subset of AB

What will happen if 2 What will happen if 2 rays have the same rays have the same

starting point?starting point?

AB and AC are 2 rays having the same starting point A ..they made an

angle

A B

C(

side)

(side)(the vertex of the angle)

The measuring of the angle:

The angle is measured (by using the protractor)

With degree unit) ° ( The measure of ^BAC is written..

m (^BAC )

The type of angles: ①zero angle

CA B

Its measure = 0°

Its sides are coincident.

②Acute angle

A C

B

Its measure is more than 0° and less than 90°

0° m (^BAC) 90 °

③Right angle

Its measure is 90°

m (^BAC) = 90 °

B

A C

④Obtuse angle

A C

B

Its measure is more than 90° and less than 180°

90° m (^BAC) 180 °

⑤Straight angle

CAB

Its measure is 180°Its sides are forming one straight line.

m (^BAC) = 180 °

⑥Reflex angle

B

A C

Its measure is more than 18° and less than 360° 180° m (^BAC) 360 °

Example: Mention the type of each of the

angles which their measures are as follow 32°

90° 110°

180° 250°

159°⅜

32° ►acute 90° ►Right 110° ►Obtuse

180° ►straight

250° ►reflex 159⅜° ►obtuse

Solution:

GOo0oOo0d

We almost finished….

Exercise: Define the type of each angle in the

following shape

6

2

3

4

5

17

Try to solve them in Try to solve them in your note bookyour note book

H.WWork book p.26:Ex.1-20And page 28

Miss Magda is proud of her students

Excellent

Bye…byeBye…bye