Question

Which statements are true about the triangle? Select all that apply.

The triangle is acute.
The triangle is obtuse.
It is an isosceles triangle.
It is a scalene triangle.
It is an equilateral triangle.
The angles add up to 180°.

Answer 1

The triangle is obtuse.

It is an isosceles triangle.

The angles add up to 180°.

Explanation:

Correct statements and reasons are in bold.

The triangle is acute. No, since one angle is obtuse.

The triangle is obtuse. Yes, because it has an obtuse angle.

It is an isosceles triangle. Yes, because 2 sides are congruent.

It is a scalene triangle. No, since 2 sides are congruent.

It is an equilateral triangle. No, since not all sides are congruent.

The angles add up to 180°. Yes because that is true for every triangle.

Answer 2

The triangle is obtuse.

It is an isosceles triangle.

The angles add up to 180°.

Explanation:

Obtuse triangles are defined as triangles with one angle obtuse angle over 90°. This triangle has an angle of 100°, so it is an obtuse triangle!

Isosceles triangles have 2 equal sides. The two orange dashes on the left and right legs of the triangle tell us they are equivalent, so this is an isosceles triangle as well!

Finally, all triangles add up to 180°! We can prove this by adding the angles.

40° + 40° = 80°

100° + 80° = 180°