Exercise 1 Page 646

Let's analyze the given triangle.

To classify the triangle by its sides, we need to know how many sides are congruent.

Note that there are markers on two sides. They indicate that these sides are congruent. Knowing this, the triangle is isosceles. Now let's look at the angles.

We can see that all three angles are acute. This allows us to classify the triangle as an acute triangle. Therefore, the given triangle is an acute isosceles triangle.