Adjacent angles formed by two intersecting lines are what?

Adjacent angles formed by two intersecting lines are what?

• A. Congruent
• B. Complementary
• C. Supplementary
• D. Linear

Answer: (C)

When two lines cross, adjacent angles share a vertex and a side, and the other two sides form a straight line. That straight line measures 180 degrees, so the two adjacent angles together add up to 180. They are therefore supplementary. Congruent isn’t guaranteed for adjacent angles—only vertical angles are guaranteed to be equal, and complementary (sum 90) doesn’t apply here. The idea of a linear pair is related—the non-common sides form a line—but the property described by the question is that their measures sum to 180.

When two lines cross, adjacent angles share a vertex and a side, and the other two sides form a straight line. That straight line measures 180 degrees, so the two adjacent angles together add up to 180. They are therefore supplementary.

Congruent isn’t guaranteed for adjacent angles—only vertical angles are guaranteed to be equal, and complementary (sum 90) doesn’t apply here. The idea of a linear pair is related—the non-common sides form a line—but the property described by the question is that their measures sum to 180.