Triangles Geometry Mr. Zampetti Unit 3, Day 1. Today’s Objectives To learn new strategies that will help find the measures of angles in a triangle To.

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Presentation transcript:

Triangles Geometry Mr. Zampetti Unit 3, Day 1

Today’s Objectives To learn new strategies that will help find the measures of angles in a triangle To learn how to classify triangles

Triangle Activity 1.Draw and cut out a large triangle. 2.Number all three angles of the triangle 3.Tear of the angles 4.Place the 3 angles adjacent to each other to form one angle Compare your results with a partner. Make a conjecture about the sum of the angles of a triangle.

Theorem 2-1 Triangle Angle-Sum Theorem The sum of the measures of the angles of a triangle is 180 .

Video: Sum of the Angles of a Triangle

Find the measure of the missing angle x x

Practice Find all Variables:

Practice Find all Variables:

Practice Find all variables

Definition Exterior Angle: an angle formed by the side of a polygon and an extension of a side.

Definition Remote Interior Angle: the two nonadjacent interior angles to an exterior angle.

Activity! Draw a triangle with an Exterior Angle like this: Measure all of the angles. With a partner, make a conjecture about the exterior angle and the remote interior angles.

Theorem 2-2 Exterior Angle Theorem The measure of each exterior angle of a triangle equals the sum of the measures of its two remote interior angles.

Find the measure of the missing angle

Find the measure of the missing angle

Definition Corollary: a statement that follows directly from a theorem.

Corollary to Theorem 2-2 The measure of an exterior angle of a triangle is greater than the measure of either of its remote interior angles.

Types of Triangles (by sides) Equilateral Isosceles Scalene

Equilateral Triangles Definition: –A triangle with three congruent sides. Example:

Isosceles Triangles Definition: –A triangle with two congruent sides. Example:

Scalene Triangles Definition: –A triangle with no congruent sides. Example:

Types of Triangles (by angle) Equiangular Acute Right Obtuse

Equiangular Triangles Definition: –A triangle with three congruent angles. Example:

Acute Triangles Definition: –A triangle whose angles are all acute. Example:

Right Triangles Definition: –A triangle with one right angle. Example:

Obtuse Triangles Definition: –A triangle with one obtuse angle. Example:

Triangle Video Triangle video!!

Homework Work Packet: Triangles