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10 Examples of Supplementary Angles

October 11, 2023
written by Rida Mirza

In mathematics, two angles are supplementary if the sum of their measures equals 180 degrees. Supplementary angles always add up to 180° and are formed when two lines intersect.

In this article, we will discuss ten examples of supplementary angles.

image showing examples of supplementary

Examples of Supplementary Angles

These are 10 examples of supplementary angles:

1: Linear Pair of Angles

Adjacent angles formed when two lines intersect are supplementary.

For example, if two lines intersect and form angles of 115° and 65°, they are supplementary because 115° + 65° = 180°.

2: Vertically Opposite Angles

Vertically opposite angles formed by two intersecting lines are always supplementary.

For example, if two lines intersect to form angles of 40° and 140°, they are supplementary vertically opposite angles.

3: Alternate Interior Angles

Alternate interior angles formed when a transversal line intersects two parallel lines are supplementary angles.

They always add up to 180°.

4: Corresponding Angles

Corresponding angles formed by a transversal intersecting parallel lines are supplementary.

They add up to 180° even though they are on different sides of the transversal.

5: Adjacent Complementary Angles

Adjacent angles that add up to 90° are complementary.

Two complementary angles that form a right angle are also supplementary (90° + 90° = 180°).

6: Angles Formed by Parallel Lines Cut by a Transversal

When a transversal cuts two parallel lines, consecutive interior angles add up to 180°, making them supplementary.

7: Adjacent Angles Around a Point

Adjacent angles around a point on a straight line add up to 360°. Adjacent angles that share a common ray are supplementary (180° each).

8: Angles in a Triangle

Three angles in a triangle always add up to 180°, so any two angles in a triangle are supplementary angles.

9: Base Angles of an Isosceles Triangle

Two base angles in an isosceles triangle have equal measures and add up to 180°, making them supplementary.

10: Same Side Interior Angles

Same side interior angles formed between two parallel lines cut by a transversal are supplementary (they add to 180°).

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