Triangles Examples

Which of the following triangles is an obtuse isosceles triangle?

a)

b)

c)

d)

Triangle c is an obtuse isosceles triangle. It's obtuse because one angle is greater than 90°, and it's isosceles because two of the three sides are the same length.

Classify this triangle based on its sides and angles.

This triangle has a right angle in it so we know that it's a right triangle.

It has two equal sides so it's also an isosceles triangle.

This lucky winner is a right isosceles triangle.

What is the measure of each angle in a regular triangle?

Regular triangles are equilateral and equiangular. All three sides are the same length and all three angles are the same size.

We know that the interior angles of a triangle always add up to 180°.

Since the three angles are equal, and they all add up to 180°, each angle must be 60°.