Classifying Triangles Angles of Triangles Sections 4 1

Classifying Triangles & Angles of Triangles Sections 4 -1 & 4 -2

v. A triangle is the figure formed by 3 segments joining 3 noncollinear points. Each of the 3 points is a vertex. The segments are the sides. A C B

Classifying Triangles by Sides Scalene Triangle – no sides congruent Isosceles Triangle – At least 2 sides congruen Equilateral Triangle – All sides congruent

Classifying Triangles by Angles 700 500 Acute – 3 acute angles 600 Right – 1 right angle 400 1200 Obtuse – one obtuse angle 600 600 Equiangular – all angles congruent

Parts of an Isosceles Triangle vertex angle leg base angles leg

Angle Sum Theorem v. The sum of the measures of the angles of a triangle is 180. 1000 400

Third Angle Theorem v If 2 angles of one triangle are congruent to 2 angles of another triangle, then the third angles are congruent.

Corollaries statements that can be easily proved using a theorem v Each angle of an equiangular triangle has measure 60. v In a triangle, there an be at most one right angle or obtuse angle. v The acute angles of a right triangle are complementary.

Exterior Angle Theorem v. The measure of an exterior angle of a triangle equals the sum of the measures of the 2 remote interior angles. Remote interior angles 350 Exterior 750 400

Joke Time v. What has wings and solves number problems? v. A mothematician

v. What did one math book say to the other math book? v. Don’t bother me! I’ve got my own problems!

v. What would a math student say to a fat parrot? v. Poly-no-mial