 ## Grade 4 Math: Geometry: Angles and Lines, Part 2

### Classifying Angles Visually

In this lesson, three types of triangles are defined, and students learn to identify these types of triangles visually.

A right triangle is defined as any triangle that has a right angle in it. For any right triangle, the remaining two sides must be acute angles. This is illustrated visually. This means that any right triangle has one right angle and two acute angles.

An obtuse triangle is a triangle that has an obtuse angle. For any obtuse triangle, the remaining two sides must be acute angles. This is illustrated visually. This means that any obtuse triangle has one obtuse angle and two acute angles.

An acute triangle is a triangle that has three acute angles. If a triangle does not have a right angle or an obtuse angle, it must have three acute angles. This is illustrated visually. That means that any acute triangle must have three acute angles.

In this lesson, students learn to recognize and classify triangles as one of these three types visually.

### How to Measure Angles Using a Protractor

The design and use of a protractor is illustrated visually. A virtual protractor is used to illustrate the measurement of angles.

### Classifying Angles and Triangles Using a Protractor

In this lesson, students learn to measure angles on screen using a virtual protractor.

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