Measurements of Common Angles/Reflex Angle

Theorem

A reflex angle measures $\theta$, where:

$180 \degrees < \theta < 360 \degrees$

or:

$\pi < \theta < 2 \pi$

Proof

A reflex angle is defined to be an angle whose measure is between that of a straight angle and a full angle.

A straight angle measures $180 \degrees$ or $\pi$ and a full angle measures $360 \degrees$ or $2 \pi$.

Hence the result.

$\blacksquare$

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): angle
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): angle