Definition:Obtuse Angle
From ProofWiki
Definition
An obtuse angle is an angle which has a measurement between those of a right angle and a straight angle.
As Euclid defined it:
- An obtuse angle is an angle greater than a right angle.
(The Elements: Book I: Definition $11$)
Note that Euclid did not consider the concept of reflex angles.
The measurement $\theta$ of an obtuse angle is such that $90^\circ < \theta < 180^\circ$ or $\dfrac \pi 2$ rad $< \theta < \pi$ rad.
