Acute angle

An acute angle ("acute" meaning "small") is an angle smaller than a right angle. The range of an acute angle is between 0 and 90 degrees, or between 0 and $\frac{π}{2}$ radians. Angles larger than a right angle (90 degrees) are called obtuse. They are found exclusively in Quadrant I or a graph, due to the terminal arm not being able to leave this Quadrant without becoming too large.