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180-degree angle is exactly half of the full angle (360-degree angle). A real-life illustration of a 180-degree angle is an ideal model is an angle between the two hands of a clock at 6 o'clock. The angle between the two hands of the clock is 180° on the basis that it frames a straight line.
- A 180-degree angle is a straight angle.
- It is exactly half of a revolution.
- It is also called a half-circle angle.
- A straight angle is created by a straight line.
- The two arms of the angle which are making 180 degrees are only opposite to one another from the normal vertex.
| Table of Content |
Key terms: 180-degree angle, Straight Line, 180-Degree Angle with a Protractor, 180-Degree Angle Using a Compass
What is a 180-degree Angle?
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The angle which forms a straight line is called the 180-degree angle. In geometry, we have different kinds of angles, like acute angles, obtuse angles, right angles, straight angles, reflex angles, and full rotation. The angle which estimates 180 degrees is named the straight angle. A 90-degree angle is half of a 180-degree and it is called a right angle. Different angles are given here:
- Acute angle: The angle which is more than 0° and under 90°.
- Right angle: The angle which is equal to 90°.
- Obtuse angle: The angle which is more than 90° but less than 180°.
- Reflex angle: The angle which is more than 180°.
- Full rotation angle: The angle equal to 360°.
180 Degree Angle Name
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An angle that measures 180 degrees is called a straight angle. At the point when we develop a 180-degree angle, it generally forms a straight line, for that reason, it is called a straight angle. There are different names for angles of different degrees.
- For instance, half of a 180-degree angle, i.e a 90-degree angle is called a right angle in geometry.
- Likewise, double 180 degrees, that is 360-degree angle is called a complete angle.
- Angles that are under 180 degrees are acute and obtuse angles.
- Two angles that together make 180 degrees are called supplementary angles.
- While at least two angles joining together at a point on a line shaping 180 degrees are called linear pairs of angles.
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Constructing a 180-Degree Angle with a Protractor
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The steps to make a 180-degree angle using a protractor are mentioned below: Stage 1: Draw a ray OA. Stage 2: Place the protractor at point B. Stage 3: In the inner circle of the protractor, search for 180° reading, and with a pencil mark a speck and name it C. Stage 4: Join O and C. Presently, ∠ABC=180 degree angle.
Constructing 180-Degree Angle Using a Compass
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Follow the given steps to make a 180-degree angle with the help of a compass. Stage 1: Draw a straight line using a ruler and name it AB Stage 2: Mark a point O between A and B. Stage 3: Take O as a middle point, and draw a circular arc of any radius with the help of a compass, the arc needs to be from the left of point O toward the right of O, or the other way around, touching the line AB. Stage 4: The circular segment cuts the straight line at two places. Mark the cuts as points C and D. Stage 5: In this way, the angle COD is 180 degrees angle.
The Theorem of Straight Line
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The straight angle theorem states that every one of the straight angles is 180 degrees. If the legs of the angle are pointing in exactly opposite directions, then it forms a straight angle. A straight angle is addressed as 180° (that is in degrees) or π (in radians).
What are the Properties of Straight Angles?
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A few important properties of straight angles are as given underneath:
- A straight angle basically measures accurately half of a revolution.
- A straight angle is delivered by rotating one ray by 180 degrees to another ray.
- At any straight angle, the arms reach out on the opposite bearings.
- A straight angle can be constructed by joining any two right angles.
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| Related Topics | ||
|---|---|---|
| Alternate Angles | Linear Pair of Angles | Properties of Parallel Lines |
| Linear Pair Axiom | Angle between Two Lines | Types of Angle |
Things To Remember
- The 180-degree angle is called a straight angle, half-circle, or semi-circle.
- A 180-degree angle can be constructed with a protractor or a compass.
- The straight angle theorem states that every one of the straight angles is 180 degrees. If the legs of the angle are pointing in exactly opposite directions, then it forms a straight angle.
- A straight angle is addressed as 180° (that is in degrees) or π (in radians).
Sample Questions
Ques.1: If a straight angle is divided into two sections, and one angle estimates 60 degrees, then track down the other angle. (2 marks)
Ans: Let the unknown angle be x Given, another angle = 60° since Straight angle = 180° Accordingly, x+60 = 180 x = 180 - 60 x = 120° Consequently, the other angle estimates are equal to 120°.
Ques.2: Two angles are supplementary. Assuming that one angle is equal to 45 degrees, track down the other angle. (2 marks)
Ans: Given, two angles are supplementary, subsequently the sum of the two angles frames a 180-degree angle. We know one angle is 45 degrees. Let the other angle be x. Hence, 45 + x = 180 {Supplementary angles sum up to 180 degrees} x = 180 - 45 = 135 degrees.
Ques.3: In case the two angles are equal to one another and are also supplementary, track down the angles. (2 marks)
Ans: Given, two angles are equal. Let the angles be x. Additionally, given two angles are supplementary, in this way, x + x = 180° 2x = 180° x = 180/2 x = 90° Hence, the two angles are 90° each.
Ques 4. What number of 180 Degree Angles does it take to Make a Full Turn? (2 marks)
Ans. 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, subsequently, two times or twice of 180-degree angle gives a full turn.
Ques 5. Angles A, B, and C make a straight angle together. Track down the measurement of angle C if angle A is 30° and angle B is 90°. (2 marks)
Ans: We know that a straight angle is a 180° angle. Hence, angle A + angle B + angle C = 180 degrees. 30° + 90° + C = 180° C = 180° - 90° - 30° = 60° Thus, the measurement of angle C is 60°.
Ques 6. What is 180 Degree Angle Called? (2 marks)
Ans. The 180-degree Angle is called a straight angle. The sides of the angle are opposite to one another and they make a straight angle on a straight line through the vertex. The presence of a 180-degree angle is a straight line.
Ques 7. Is a 180 Degree Angle Obtuse? (2 marks)
Ans. The proportion of an obtuse angle is more than 90° yet under 180°, in this way, a 180-degree angle is definitely not an obtuse angle. It is called a straight angle.
Ques 8. What are 180 degrees for a triangle? (2 marks)
Ans. For a triangle, the amount of interior angles is equal to 180 degrees. Likewise, the sum of every interior angle and exterior angle of a triangle is 180 degrees. In this manner, the sets of an interior angle and exterior angle of a triangle make a straight angle.
Ques 9. Is a line 180 degrees? (2 marks)
Ans. A straight angle generally forms a straight line. The measurement of the straight angle is 180°. The arms of the straight angle lie opposite to one another from the vertex point.
Ques 10. What does a 180-degree angle represent? (2 marks)
Ans. A straight line makes a 180-degree angle. It is equal to a half rotation around a full circle. A straight line that is a 180-degree angle is equal to 3/4 of a pivot around a circle. A round trip makes a 360-degree angle.
Ques 11. If a 180-degree angle is partitioned into two sections, and one angle estimates 80 degrees, then what is the other angle? (2 marks)
Ans: Let the angle be b and the given angle is a = 80°. a + b = 180° 0° + b = 180° b = 180° - 80° = 100° Consequently, the other angle is 100°. It is an obtuse angle.
Ques 12. There are three angles framing a straight angle together - angle A, angle B, and angle C. If angle A = 40 degrees, angle B = 100 degrees, what is the angle of C? (2 marks)
Ans.: We know that a straight angle is a 180 degrees angle. Hence, angle A + angle B + angle C = 180 degrees. 40° + 100° + C = 180° C = 180° - 100° - 40° = 40° Hence, the measurement of angle C is 40 degrees.
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