## What Is a 180 Degree Angle?

**The 180 degree angle is an angle that forms a ****straight line****. The 180 degree angle in radians is ****or about 3.14 radians.**

You can see that the straight line is formed when the two arms of the angle (BA and BC) are opposite rays. The two arms extend in the opposite directions. Thus, the 180 degree angle is also called ‘a straight angle.’

#### Begin here

## How to Draw a 180 Degree Angle

There are two methods to draw an accurate 180 degree angle: using a compass or using the protractor.

**Constructing 180 Degree Angle Using Protractor**

**Step 1: **Draw ray OA. Align the center of the protractor with the point O. O will be the vertex of the angle.

**Step 2:** Mark the 180 degree reading (on inner calibration) as point B.

**Step 3:** Join OB.

∠AOB = 180^{o}

**Constructing 180 Degree Angle Using Compass**

Here are the steps to assist you in drawing 180 degree angle using a compass:

**Step 1:** Draw a straight line and name it PQ.

**Step 2:** Mark a point between PQ using a dot and name it as O.

**Step 3:** Place the compass on the point O and make an arc that starts on OQ and ends on OP, making a semicircle.

**Step 4:** Name the points of intersection of the arc with OP and OQ as X and Y respectively.

∠YOX = 180^{o}

#### Related Worksheets

## Negative 180 Degree Angle

The straight angle if measured clockwise is a negative straight angle (-180^{o}).

## 180 Degree Angle Name

As we mentioned earlier, the 180 degree angle forms a straight line. So, it is also known as a “Straight angle” or“flat angle.”

**Types of angles**** formed by a 180 degree angles:**

- Half of 180
^{o}angle measures 90^{o}. It is known as a right angle. - Twice the 180
^{o}angle measures 360^{o}. It is known as a complete angle or a full angle. - Angles greater than 180
^{o}and less than 360^{o}are called reflex angles. - Angles between 90
^{o}and 180^{o}are called obtuse angles.

## Facts about 180 Degree Angle

- Two angles which add up to 180 degrees are called supplementary angles.
- Angles in a linear pair always add up to 180 degrees.
- The sum of three angles in a triangle is 180 degrees because if you line them up they form a straight line.
- The hands of the clock make 180 degrees 22 times in a day.
- Hands of a clock make a 180 degree angle at 2:45, 6:00 and 12:30.
- The straight angle is half of the complete revolution.

## Conclusion

In this article, we learned about the 180 degree angle (straight angle), and its construction using protractor and compass. Let’s solve a few examples and practice problems based on the concept of 180 degree angle.

## Solved Examples on 180 Degree Angle

**Example 1: What is the measure of the angle BOC?**

**Solution:**

The straight angle is 180 degrees. Thus, two angles making a straight angle will add up to 180 degrees.

Here, ∠AOB = 40^{o}

Let us assume that ∠BOC = x.

x + 40^{o} = 180^{o}

x = 180^{o} – 40^{o}

x = 140^{o}

**Example 2: How is 180 degree angle related to a complete angle and a right angle? **

**Solution:**

A complete angle measures 360 degrees.

Half of the complete circle angle is 180 degree angle.

Right angle measures 90 degrees.

Twice the right angle is a straight angle. Two adjacent right angles form a straight angle.

**Example 3: What is the angle made by the hour hand and the minute hand when the clock reads 06:00?**

**Solution:**

## Practice Problems on 180 Degree Angle

## 180 Degree Angle - Definition, Construction, Facts, Examples, FAQs

### Which angle measures 180 degrees?

A 180 degree angle is a straight angle.

### What does a 180 angle look like?

A 180 degree angle forms a straight line.

### A straight angle is half the

A straight angle is half the complete angle.

### What is the measurement of a 180 degree angle in radians?

$180^{\circ} = \pi$ radians

## Frequently Asked Questions about 180 Degree Angle

**How do you know when an angle is 180 degrees?**

The 180 degree angle forms a straight line. Its arms form opposite rays.

**Which angles always add up to 180 degrees?**

- Angles in a linear pair
- Three interior angles of a triangle
- Two supplementary angles

**Can a right angle be used to make a straight angle?**

Yes, you can join two right angles to form a 180 degree angle.

**What is a complete angle?**

A complete angle or a full angle is 360 degree angle.