Straight Angle: Measurement, Construction, Properties & Theorems

Straight angle is an angle with the sides opposite to the vertex in the same straight line that equals two right angles. A straight angle measures 180° (half a revolution, two right angles, or π radians). The angles form a straight line that passes through the vertex. A straight angle is also known as a 'flat angle.'

Key Takeaways: Straight angle, Angle, Liens, Straight lines, Vertex, Line segments

Also read: Isosceles Triangle Theorems

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Straight Angle Measurement

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A straight angle is similar to a straight line and has an angle measurement greater than an obtuse angle. The measurement of 180° creates a straight angle between the two intersecting lines. Straight angles can be formed by connecting three points on any straight line, each of which has a coordinate value. The outside points are the endpoints of two line segments, and the middle point is the vertex where these two lines intersect at an angle of 180°.

Straight Angle

The video below explains this:

Straight Angle Detailed Video Explanation:

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Properties of Straight Angles

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Straight angles have the following important properties:

• Both sides of a straight angle are perpendicular to each other.
• Half of the rotation is completed by the straight angle.
• The degree of straightness is 1800.
• Straight angles can be created by joining two right angles together.

Also read: Collinear points

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Straight Angle Theorems

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According to the straight angle theorem, all straight angles are 180 degrees. A straight angle is formed when the legs of an angle point exactly in opposite directions. A straight angle is denoted by the symbol 180 (in degrees) or (in radians).

In geometry, one good example is a line segment, the endpoints of which extend in the opposite direction.

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Construction of Straight Angle

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The steps for making a Straight Angle are as follows:

• Using a ruler, draw a straight line OB with an arrowhead at B.

• Place the protractor on this line so that the protractor's baseline is adjusted over OB. Point B should be oriented towards the protractor's 0°.

• Mark the point starting at 0° and working your way up to 180°. When you reach 180°, make a mark on the paper with the letter A.

• Now connect the vertex of the OB line to the marked point A. The arrowhead on the second ray OA should be at A.

Also read: Minors and Cofactors

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Things to Remember

• Straight angles appear to be straight lines, but they have two arms. A straight line, on the other hand, has only one arm that points in one direction.
• When the sum of an acute angle and an obtuse angle is equal to a straight angle, those angles are considered supplementary.
• When we look at the angles within a circumference, we can see that they divide the circle into two equal halves and correspond to the circumference's diameter.
• It is the boundary between convex (acute, right, and obtuse angles) and concave angles.
• When you stretch your arms or a dancer stretches their legs you can see straight angles.

Also read: Properties of Determinants