Angles
Angles are formed by two rays sharing a common endpoint (the vertex) and are classified by their degree measure in Grade 6 math (Saxon Math, Course 1). Acute angles measure less than 90°; right angles measure exactly 90° (shown by a square corner symbol); obtuse angles measure between 90° and 180°; straight angles measure exactly 180°; reflex angles measure more than 180°. Angles are measured in degrees using a protractor. They appear in every polygon (triangle has 3 interior angles, quadrilateral has 4, etc.) and are foundational for understanding geometry, construction, and trigonometry in later math.
Key Concepts
New Concept An angle is formed where lines or rays intersect. Angles are classified as acute (less than a right angle), right (a square angle), or obtuse (greater than a right angle). What’s next Next, you’ll apply these definitions in worked examples, learning to identify and correctly name acute, right, and obtuse angles in various figures.
Common Questions
What are the main types of angles and their degree ranges?
Acute: less than 90°. Right: exactly 90°. Obtuse: 90° to 180°. Straight: exactly 180°. Reflex: more than 180°.
How are angles measured?
Angles are measured in degrees (°) using a protractor. A full rotation is 360°.
What symbol indicates a right angle in a diagram?
A small square drawn at the vertex of the angle indicates exactly 90°.
How do you classify an angle that measures 127°?
127° is between 90° and 180°, so it is an obtuse angle.
What is the sum of angles in a triangle?
The three interior angles of any triangle always sum to 180°.