An equilateral triangle has 3 sides of equal length. The dashes on the lines show they are equal in length. All of the angles are also equal. An isosceles triangle has 2 sides of equal length.

An acute angle is less than 90°. It might look small and sharp, like the corner in a slice of pizza. An obtuse angle is between 90° and 180°. It’s wider than a right angle but not a straight ...