180 Degree Angle

The 180-degree angle is a straight angle as it forms a straight line. It is exactly half of the full angle (360-degree angle). If we talk about a real-life example of a 180-degree angle, then a perfect example is the angle between the two hands of a clock at 6 o'clock. The angle between the two hands of the clock is 180° because it forms a straight line.

A 180-degree angle is a straight angle and it is exactly half of a revolution. It is also called a half-circle angle. A straight angle is produced by a straight line. The two arms of the angle which are making 180-degree are just opposite to each other from the common vertex. A 180-degree angle modifies the direction of a point. A 90-degree angle is half of the 180-degree angle and it is known as a right angle. Look at the image given below shows how a 180-degree angle looks.

In the above image, rays AO and OB share a common point O. AO and OB rays are opposite to each other. AB is a straight line and forms an angle of 180 degrees.

An angle that measures 180 degrees is called a straight angle. Whenever we construct a 180-degree angle, it always forms a straight line, that is why it is known as a straight angle. There are different names for angles of different measurements. For example, half of a 180-degree angle, i.e a 90-degree angle is known as a right angle in geometry. Similarly, double of 180 degrees, that is 360-degree angle is known as a complete angle. Angles that are less than 180 degrees are categorized as acute and obtuse angles.

Two angles that together form 180 degrees are known as supplementary angles. While two or more angles combining together at a point on a line forming 180 degrees are known as linear pairs of angles.

The 180-degree angle can be drawn with the help of a protractor and compass.

Constructing 180-Degree Angle Using a Protractor

Follow the given steps to construct a 180-degree angle with the help of a protractor:

• Step 1: Draw a ray OA.
• Step 2: Place the protractor at point O.
• Step 3: In the inner circle of the protractor, look for 180° reading and with a pencil mark a dot and name it C.
• Step 4: Join O and C. Now, ∠AOC=180 degree angle.

Constructing 180-Degree Angle With a Compass

Follow the given steps to construct a 180-degree angle with the help of a compass.

• Step 1: Draw a straight line with help of a ruler and name it AB.
• Step 2: Mark a point O anywhere between A and B.
• Step 3: Take O as a center point, draw an arc of any radius with help of a compass, the arc should be from the left of point O to the right of O, or vice-versa, touching the line AB.
• Step 4: The arc cuts the straight line at two points. Mark the cuts as points C and D.
• Step 5: Thus, the angle COD is 180 degrees angle.

Important Notes

• The 180-degree angle is also called a straight angle, half-circle, or semi-circle.
• A 180-degree angle can be constructed with a protractor or a compass.

Related Articles

Check these interesting articles related to the 180-degree angles in geometry.

• 30 Degree Angle
• 60 Degree Angle
• Measuring Angles
• 30-60-90 Triangle

What are 180-Degree Angles in Real Life?

180° angles are widely seen in real life. In everyday life, 180-degree angles are used for constructing structures, highways, houses, and sports facilities, by engineers and architects. Carpenters make benches, tables, and sofas using straight angles.

What does a 180-Degree Angle Look Like?

A 180 degree appears like a straight line because the rays or the arms of the angle making 180 degrees are completely opposite to each other. The common point joining the lines makes half revolution that is the angle of 180 degrees.

How many 180 Degree Angles does it take to Make a Full Turn?

For a full turn, we need two 180-degree angles. 360-degree angle is a full rotation or full turn. The half of 360 degrees is 180 degrees, thus, twice or two times of 180-degree angle gives full turn.

What is 180 Degree Angle Called?

The 180-degree angle is known as a straight angle. The sides of the angle are opposite to each other and they make a straight angle on a straight line through the vertex. The appearance of a 180-degree angle is a straight line.

Is a 180 Degree Angle Obtuse?

The measure of an obtuse angle is more than 90° but less than 180°, thus, a 180-degree angle is not an obtuse angle. It is called a straight angle.

How many 90 Degree Angles are in a 180 Degree Angle?

There are two 90 degrees angles in a 180-degree angle as the sum of two 90 degree angles is equal to 180 degrees.

What are 180 Degrees for a Triangle?

The sum of all the interior angles in a triangle is always equal to 180 degrees. Also, the pair of an interior angle and the subsequent exterior angle in a triangle gives a straight angle that is a 180-degree angle.