Adjacent Angles
Two angles with a common vertex and arm, with their other arms on different sides.
Key: ∠ABD + ∠DBC = ∠ABC
Key: ∠ABD + ∠DBC = ∠ABC
Linear Pair
Adjacent angles whose non-common arms form a straight line.
Key: ∠ABD + ∠DBC = 180°
Key: ∠ABD + ∠DBC = 180°
Vertically Opposite
When two lines intersect, the opposite angles are equal.
Key: ∠AOD = ∠BOC
Key: ∠AOD = ∠BOC
Intersecting Lines
Lines that cross at one point, creating four angles.
Key: Point of intersection
Key: Point of intersection
Parallel Lines
Lines that never meet and stay the same distance apart.
Key: PQ ∥ RS
Key: PQ ∥ RS