Angles
Compare and measure angles and explain their types and sum–difference relationships.
Meaning
An angle measures the opening between two rays from one point. A right angle is 90 degrees; an acute angle is between 0 and 90; an obtuse angle is between 90 and 180.
Example
At 3 o'clock, the smaller angle between the clock hands is a right angle of 90 degrees. Unequal hand lengths do not change the opening. Angle size does not depend on drawn side length. Check whether the question means the smaller or larger angle between the rays.
Practice for this concept
Scope and references
Topics
Angle measures, acute, right, and obtuse angles, vertically opposite angles, angle sums and differences
Learning goal
Compare and measure angles and explain their types and sum–difference relationships.
Helpful background
Explore the two rays forming an angle and measurement units.
Angles
These choice exercises use stated geometric conditions. They do not establish construction, drawing, spatial manipulation, written proof, or mastery of the whole geometry area.