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

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 congruent Equilateral Triangle – All sides congruent

Classifying Triangles by Angles 700 Acute – 3 acute angles 500 600 Right – 1 right angle 400 Obtuse – one obtuse angle 200 1200 600 Equiangular – all angles congruent 600 600

Parts of an Isosceles Triangle vertex angle leg leg base base angles

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

Third Angle Theorem 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 Each angle of an equiangular triangle has measure 60. In a triangle, there an be at most one right angle or obtuse angle. The acute angles of a right triangle are complementary.

Exterior Angle Theorem 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 What has wings and solves number problems? A mothematician

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

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