Triangles <ul><li>A triangle is formed by three line segments that intersect only at their endpoints. A triangle can be named by its vertices. </li></ul><ul><li>The sum of the measures of the angles of a triangle is 180°. </li></ul>C A B
<ul><li>In Δ SUN , the measure of angle S is 29°, and the measure of angle N is 99°. Find the measure of angle U . </li></ul><ul><li>The measures of the angles of a certain triangle are in the ratio 3:4:5. Find the measure of each angle. </li></ul>
Types of Triangles By Angles In an acute triangle , all the angles are acute. In an obtuse triangle , one angle is obtuse. In a right triangle , one angle is right. In an equiangular triangle , all the angles are congruent.
Types of Triangles By Sides No two sides of a scalene triangle are congruent. At least two sides of an isosceles triangle are congruent. All the sides of an equilateral triangle are congruent.
Classify each triangle by its angles and by its sides. 60° 60° 60° 60° 30°