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Lesson 4: Classifying triangles

# Types of triangles review

Review ways to classify triangles based on their sides lengths and angles.  Practice classifying triangles.

## Classifying triangles by their angles

### Acute triangles

An $\text{acute}$ triangle has $\text{3 angles that}$ . Below are examples of $\text{acute triangles}$.

### Right triangles

A $\text{right}$ triangle has and $2$ acute angles. Below are examples of $\text{right triangles}$.

### Obtuse triangles

An $\text{obtuse}$ triangle has $\text{one angle that measures}$ and $2$ acute angles. Below are examples of $\text{obtuse triangles}$.
Problem 1A
Classify $\mathrm{△}PQR$ by its angles.

Want to try more problems like this? Check out this exercise

## Classifying triangles by their side lengths

### Equilateral triangles

An $\text{equilateral}$ triangle has $\text{three equal sides}$. Below are examples of $\text{equilateral}$ triangles.

### Isosceles triangles

An $\text{isosceles}$ triangle has $\underset{―}{\text{at least}}$ $\text{two equal sides}$. Below are examples of $\text{isosceles}$ triangles.

### Scalene triangles

A $\text{scalene}$ triangle has $\text{no equal sides}$. Below are examples of $\text{scalene}$ triangles.
Problem 2A
Classify $\mathrm{△}PQR$ by its sides.