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Acute Angle, Obtuse Angle and Reflex Angle

You must have a fun on a slide in a park or garden. Observe the
angles made between the slope and the ground or on the slope itself.
Can you say which types of angles are marked as ∠1 and ∠2 in the
picture given here?
We are unable to answer this question by just knowing 2
about right and straight angles because these do not 1
have L shape (right angle) or a straight edge (straight
angle).
Here, ∠1 is smaller than a right angle (90°). Such angles are called acute angles. ∠2 is greater than
a right angle, and such angles are called obtuse angles.
The measure of an acute angle lies between 0° and 90°, while an obtuse angle lies between 90° and
180°.

Let us now consider the angle formed by
7 out of 8 pieces of a pizza. Angle Poem
Angles are easy, peasy, lemon squeezy

Just remember acute angles measure the smallest
Right angles stand the tallest
Straight angles are like lines

That measure 180° all the time
Don’t forget obtuse angles are really fat
Wait! That is so funny… Who does that?

What do we call an angle measuring greater than 180°? Such an angle is called a reflex angle. The
measure of a reflex angle lies between 180° and 360°.
All the types of angles can be summarised in the following table:

Angle Diagram Definition Example
(Angle between hour
and minute hands)
Zero An angle whose measure is 0°, is 11 12 1
angle called a zero angle. 10 2
9 3
8 4
0° 7 6 5

At 12 midnight, a 0°
angle is formed.

Acute An angle whose measure is less than 11 12 1
angle 90° is called an acute angle. 10 2
9 3
8 4
30° 7 6 5

At 1 o’clock, a 30° angle
is formed.

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