Ontario Mathematics Proficiency Practice Test

An obtuse angle is defined as an angle that is greater than 90 degrees but less than 180 degrees. This categorization helps distinguish obtuse angles from other types, such as acute angles, which are less than 90 degrees, and right angles, which are exactly 90 degrees.

The range for obtuse angles means that they open wider than a right angle, reflecting a greater degree of rotation from the initial position of the angle's two rays. Therefore, any angle falling within this specific range, where it exceeds the value of 90 degrees but does not reach 180 degrees, is accurately considered obtuse.

The other statements describe different classifications of angles: angles less than 90 degrees describe acute angles, an angle equal to 180 degrees is classified as a straight angle, and angles greater than 180 degrees are known as reflex angles. Each of these categories is important for understanding the complete spectrum of angle types, but they do not accurately describe the defining characteristics of an obtuse angle.