Straight Angle Definition
Different Types of Angles
According to the different measures of an angle, an angle is divided into 6 different types.

Acute Angle

Obtuse Angle

Right Angle

Straight Angle

Reflex Angle

Full Angle
In this topic, we will study straight angles in detail. We will learn its definition, properties, and examples.
Properties of Straight Angles
Some important properties of straight angles are as follows:

In a straight angle, both sides of the angle are opposite to each other.

The straight angle completes half of the rotation.

The straight angle degree is 1800.

Straight angles can be formed by joining to right angles.
How to construct a Straight Angle Diagram?
The steps to construct a Straight Angle Diagram are as follows:

Draw a straightline OA using a ruler, with O as the vertex of an angle

Now place the protractor on this line such that the baseline of the protractor is over OA. The point A should be at 00 of the protector.

Now starting from 0° move towards 180 degrees, On reaching 180°, mark a point B there.

Now join the points O and B. we get another side of an angle opposite to OA. thus forming a straight angle.
Points to Remember:

The measure of a straight angle is always 1800.

When we move anticlockwise the straight angle measures + 1800.

When we move clockwise the straight angle measures – 1800.

The arms of an angle face opposite to each other.
Let us understand the concept of straight angle by straight angle examples
Solved Examples:
Example 1:
Identify the straight angle in the below figure.
Solution: (image will be uploaded soon)
Angle BOD is a straight angle because it measures 1800, and it is formed by the addition of two right angles i.e. ∠COB + ∠COD = 1800. Also it forms a straight line.
Example 2: At what time is the angle between the hands of a clock exactly one straight angle?
Solution: At 6 o’clock.
Example 3: In the given figure, ∠AOB is a straight angle, ∠AOC = 68°, and ∠BOC = x°.
Find the value of the x.
Solution: As given that ∠AOC = 680 and ∠AOB is straight angle
We know that straight angle measures 1800
Therefore,
∠AOB = ∠AOC + ∠ BOC
1800 = 680. + x
x = 180 – 68
x = 1120
Hence x = 1120
Example 4: In the given figure, ∠AOB is a straight angle, ∠AOC = (3x+20)° and ∠ BOC =(4 x36)°. Find the value of the x.
Solution:
As given that ∠AOC = (3x + 20)0 and ∠BOC = (4x – 36)0 and ∠AOB is straight angle
We know that straight angle measures 1800
Therefore,
∠AOB = ∠AOC + ∠ BOC
1800 = (3x + 20) . + ( 4x – 36)
180 = 7x – 16
7x = 180 + 16
x = 196/7
x = 28
Hence x = 280
Quiz Time

In the given figure , AOB is a straight angle, ∠ AOC = (3x8)° and ∠COD =50 and ∠BOD° =(x+10)°. Find the value of the x.

Two angles form a straight angle. The measure of one of its angles is 62°. Find the other angle.
Fun Facts

The word angle was discovered from the Latin word of angulus, It means corner.

An angle was the space or interval between intersecting lines was supposed by Carpus of Antioch.

The straight is an angle which is equal to 1800 or ½ turn.

A perigon is also called a complete angle, or a full angle. It has 3600 or a complete 1 turn.
1. Is a Triangle a Straight Angle?
Answer: No, a triangle cannot be a straight angle.
As we know that the sum of the measures of the angle of a triangle is 1800 and also from straight angle definition straight angle measures 180^{0}, but we cannot consider a triangle as a straight angle because a triangle is an enclosed figure and a straight angle is in the form of a straight line.
Triangle is a closed figure with three sides and three vertices, while a straight angle has collinear points so that it cannot form a closed figure.
Hence a triangle and straight angle are different.
2. What are the RealLife Straight Angle Examples?
Answer: Some of the straight angle examples are:

A plane inclined staircase forms a straight angle

The angle formed in a seesaw is straight.

Any flat surface has an angle of 180^{0}.

A straight stick has a straight angle which is 180^{0}.

A clock hand makes a straight angle at 6 o’clock.
3. What is Half of a Straight Angle?
Answer: According to straight angle definition an angle is a straight angle if it measures 180^{0}. Half of the straight angle is 90^{0}, and which represents a right angle. Therefore half of a straight angle is the right angle. Two right angles can form a straight angle.
4. Is a Straight Angle a Reflex Angle?
Answer: According to straight angle definition an angle is a straight angle if it measures 180^{0}. And according to reflex angle, an angle whose measure is greater than 180^{0} and less than 360^{0} is called a reflex angle. Therefore a straight angle is not a reflex angle.