4.1. Triangle Sums http://www.ck12.org
A Little Triangle Review
Recall that a triangle can be classified by its sides.
Scalene: All three sides are different lengths.
Isosceles: At least two sides are congruent.
Equilateral: All three sides are congruent.
By the definition, an equilateral triangle is also an isosceles triangle.
And, triangles can also be classified by their angles.
Right: One right angle.
Acute: All three angles are less than 90◦.
Obtuse: One angle is greater than 90◦.
Equiangular: All three angles are congruent.