121
Angles
Textbook Part 4, pp. 22–23
GoalMeet rays and angles; tell right, acute and obtuse angles apart.
New words
ray · nurangle · burchakright angle · to‘g‘ri burchakacute angle · o‘tkir burchakobtuse angle · o‘tmas burchak
Explanation
A part of a line that has a start but no end is a ray. Two rays starting from one point make an angle. The corner of a notebook page is a right angle. A smaller angle is acute; a bigger one is obtuse.
Worked examples
At 3:00 the clock hands make a right angle.
Slightly open scissors make an acute angle; a laptop opened wide makes an obtuse angle.
Class activity
“Angle checker”: children fold a paper twice to make a right angle and test corners around the room: right, acute or obtuse.
Practice
1
How many ends does a ray have?
One (a start, no end)
2
What kind of angle is a book cover’s corner?
A right angle
3
What is an angle smaller than a right angle called?
Acute
4
How many right angles does a square have?
4