LESSON PLANNING OF USE PROTRACTOR TO CONSTRUCT ANGLES OF DIFFERENT MEASURES

Subject Mathematics

Grade 5^{th}

Students` Learning Outcomes

- Use protractor to construct, right angle, straight angler and reflex angles of different measures

Information for Teachers

- A protractor is a tool, typically made of transparent plastic, for measuring angles. Protractor is used to measure angles in degrees (
^{0}) in geometry lessons in schools. -
- The circle outside an angle`s arms is termed as Exterior Angle.
- The exterior angle of an obtuse angle or acute angle is known as Reflex Angle.
- A Reflex Angle is one which is more than 1800 but less than 3600

- Consult text book at all steps where and when required.

Material / Resources

Writing board, chalk / marker, duster, geometry box, textbook

Introduction

- Ask students if they have seen sun rise or sun set?

- Draw a straight line on board and make half sun and ask how it looks at this time [show sample to the students].
- Tell them to open their geometry box and see if there is something resembling that.

- Let them explore that the shape of protractor resembles a half sun.
- Ask them to DRAW SUNRISE by using protractor, the way you drew on the board. [Show sample]
- Let them try, later helping them to draw on the board with the help of a protractor.
- Ask them to read and find total number of degrees on this D- shaped tool.
- May be they will answer 180
^{0}or something else. - Tell them that this is also an angle called straight angle.
- Tell the students that there are 180
^{0}degrees in a straight angle. Ask students if they have ever heard the phrase “does a one-eighty”. It means to do things in opposite direction. - Let them try to join two protractors in a way to complete a whole circle and then ask then count number of degrees it has.
- Let them explore that there are 360
^{0}degree in a circle.

Development

Activity 1

- Recall the concepts of angles which they have already studied in Grade 4
- Conduct one or two activities from previous grade if you find necessary.
- This will help to create a link.
- Make angle 4 of 180
^{0}by the hands of the clock; make the figure then change 4 directions. - Encourage students to get ready for the game: Do as I do?
- Attempt following steps on board and ask students to do the same individually.

- Place the center of protractor at a point A which is point O.
- Look for the number 180
^{0}on protractor and mark a point on the paper next to 180^{0} - Take away the protractor and label the point C.
- Join point A and new point C by using ruler.

- Relate the clock hands and angles that 12 0` Clock is a Zero degree angle and 6 0` Clock is 180
^{0}angle. [Change the direction of Minute and Hour hand to form new angle]

Sum up / Conclusion

- Ask students what they have learnt during the period about the angles.
- Student will answer that angle of 180
^{0}is called straight angle.

- Reflex Angle is one which is more than 180
^{0}but less than 360^{0 }

- Reflex angle is larger angle, whereas its smaller angle may be acute or obtuse.

Assessment

- Give angles of different degrees to the students and ask them to draw them and identify its type.

i. 45

^{0}ii. 170

^{0}iii. 90

^{0}iv. 20

^{0}v. 180

^{0}vi. 360

^{0}

Follow up

- Ask students to look for examples that show straight and reflex angles in their surroundings.

- Added 180
^{0}in the noted angle that would be the required reflex angle, For example 45^{0}+ 180^{0}= 225^{0} - Reflex angle will be 180
^{0}