zero angle — Definition, Formula & Examples
A zero angle is an angle that measures exactly 0°. Both rays point in the same direction and lie right on top of each other, so there is no opening between them.
A zero angle is an angle formed by two rays that share a common endpoint (vertex) and extend in the same direction, resulting in a measure of 0 degrees.
Example
Problem: A door is completely closed and flat against the wall. What is the angle between the door and the wall?
Step 1: Picture the wall as one ray and the edge of the door as the other ray. Both start at the hinge (the vertex).
Step 2: When the door is fully closed, it lies flat against the wall. The two rays point in the same direction with no gap between them.
Step 3: Since there is no opening, the angle measures 0°.
Answer: The angle between the closed door and the wall is a zero angle, measuring 0°.
Why It Matters
A zero angle completes the family of angle types you learn in geometry: zero, acute, right, obtuse, straight, and reflex. Recognizing it helps when measuring rotations, since a full turn starts and ends at 0°.
Common Mistakes
Mistake: Confusing a zero angle (0°) with a straight angle (180°).
Correction: In a zero angle both rays overlap going the same way. In a straight angle the rays point in opposite directions, forming a straight line.