Straight Angle (original) (raw)
Last Updated : 23 Jul, 2025
**A straight angle measures 180° and looks as it is a straight line, therefore, it is a mathematical way of expressing a straight line. The two rays of the 180-degree angle are subtended towards the opposite direction, where the rays are joined to each other at endpoints.
Well, that's what we call a straight angle. It's just like a flat line that goes straight ahead. This angle is not only easy to visualize but also serves as a reference point for various geometric principles.
In this article, we will learn about **Straight Angles by briefly learning about angles and their types.
Table of Content
- What are Angles?
- What is a Straight Angle?
- How many degrees in a Straight Angle?
- Real-Life Examples of Straight Angle
- Construction of Straight Angle
- Straight Angle in Pair
- Straight Angle Examples
- Practice Questions on Straight Angle
What are Angles?
An angle is a geometric figure that represents the amount of rotation or deviation between two straight lines, rays, or line segments that meet at a common endpoint. The angle is denoted by the symbol “∠”.
What is a Straight Angle?
A **straight angle is an angle that measures exactly 180 degrees (°). It is formed when two rays or lines point in exactly opposite directions, creating a straight line.
Straight Angle Definition
"Straight angle is defined as an angle that measures exactly 180°.
A straight angle is typically denoted as 180° or π radians (π rad)." When two rays meet and align in the same direction then the angle between them is 180° which is called a Straight Angle. We can understand from the name that since the rays are in a straight line hence it is called Straight Angle.
How many degrees in a Straight Angle?
A straight angle is an angle equal to 180°. It looks like a straight line. We know that an angle is formed when two rays meet. When two rays meet to form a Straight Angle which is equal to 180° then it can be seen that they are in one direction forming a Straight Line and hence called Straight Angle.
Properties of a Straight Angle
The different properties of Straight Angle are listed below:
- A straight angle always measures 180°.
- Straight angles create a straight line.
- It is denoted by π (i.e. π = 180°).
- It is also called the angle of a straight line.
- The two rays form a straight angle point in precisely opposite directions.
- It can be formed by joining two right angles (i.e. 90° + 90° = 180°)
Real-Life Examples of Straight Angle
We can find many objects around us forming a Straight Angle. Let's see some real-life examples of Straight Angle around us:
- **6 O'Clock: The minute hand on a clock points to the 12 at 12 o'clock and to the 6 at 6 o'clock, forming a straight line.
- **Pencil: The body of a standard pencil is a straight line, extending from the eraser at the top to the tip at the bottom.
Straight Angles are applicable in real life in following:
- Architectural Precision
- Engineering Designs
- Art and Design Aesthetics
- Mathematics Education
- Optics and Physics
- Computer Graphics
Construction of Straight Angle
Construct a straight angle i.e., 180° angle, you can follow these steps using a protractor and a ruler:
**Step 1: Using the ruler, draw a straight line ****(OA)** horizontally across the paper.
**Step 2: Take your protractor and align its center (the hole) with point O on your baseline.
**Step 3: Extend the protractor's arm (the straight edge of the protractor) along line OA. Ensure
Mark a point at 180° on the protractor's scale. This point is directly opposite the center (point O) on the other side of the line OA.
**Step 4: A to the point you marked at 180° on the protractor's scale. This line will form a straight angle with line AB.
Label the points where the two lines intersect, say, points A and B, to indicate that it's a straight angle.
Straight Angle
Finally, a straight angle is constructed, which is a 180° angle.
Straight Angle in Pair
A straight angle pair, also known as a linear pair of angles, consists of two angles that combine to form a straight line. The sum of the measures of these two angles is always equal to 180°.
In other words, ∠AOC + ∠BOC = 180° i.e. **∠1 + ∠2 = 180°
**Also Check:
Straight Angle Examples
**Example 1: If you add a straight angle to a 60°, what will be the total angle measure?
**Solution:
As we know, Straight Angle =180°
⇒ 60° + 180° = 240°
**Example 2: There are two angles on a straight line if one of its angles is 75 °. Find another one.
**Solution:
Let the angle be x ;
Given: another angle = 75°Sum of all angles in the straight line is 180°
∴ x + 75 =180
∴ x = 180 - 75 = 105°
**Example 3: Find the value of 'x' in the given figure below
**Solution:
Given that,
Given: ∠AOC = 50° and ∠BOC = x
In the fig we can see that ∠AOB is straight angle i.e. 180°
∠AOB = ∠AOC + ∠BOC
⇒ 180° = 50 + **x
⇒ x = 180° - 50°
⇒ x = 30°
**Example 4: Find the value of ' x ' in given figure below, where O is the centre of circle.
**Solution:
Given;
∠COD = 90° ( right angle )
∠BOD = 50°
∠AOC = xIn the fig we can see that ∠AOB = 180° ( angle of straight line )
∠AOC + ∠COD + ∠BOD = ∠AOB
putting values, we getx + 90° + 50° = 180°
⇒ x = 180° - ( 90° + 50° )
⇒ x = 180° - 140°
⇒ x = 40°
Practice Questions on Straight Angle
**1. Draw an Straight Angle and label its angle.
**2. If you add a straight angle to a right angle, what will be the total angle measure?
**3. Draw a simple picture of a straight angle. Label it and write down its degree measure.
**4. Look around your room or outside your window. Can you find any objects or shapes that have straight angles? List a few examples.
**5. Find the value of x.
