TOPIC 6 · GRADE 4 FOUNDATION
Angle Types and Benchmark Turns
Compare turns with 90° and 180° to classify acute, right, obtuse, straight, and reflex angles.
MA.4.GR.1.1BIG IDEA
An angle measures rotation around its vertex. A square corner is 90°, a straight turn is 180°, and a full turn is 360°.
WHAT TO KNOW
- Acute angles are less than 90°; right angles equal 90°.
- Obtuse angles are between 90° and 180°; straight angles equal 180°.
- Reflex angles are greater than 180° but less than 360°.
WATCH OUT
The lengths of the drawn sides do not affect angle measure.
TRY IT
Drag the angle control through a full turn and predict the classification before reading it.
Choose the next topic from the lesson rail when you are ready.