This means two of the angles are equal. These are the base angles. The base angles are opposite the equal sides. An equilateral triangle has three equal sides. This is shown by the hatch marks on ...

You can see it's an acute angle, so it's less than 90°. Image caption, Find the base line on the protractor (it's marked 0° at one end and 180° at the other end). Place the middle of the base ...