Triangles and Isosceles Sum of angles and properties of isosceles.

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Presentation transcript:

Triangles and Isosceles Sum of angles and properties of isosceles

Triangle Sum Conjecture Conjecture – a generalization resulting from inductive reasoning Sum of angles of a triangle =180 Can you prove this without using a protractor

This is on page 201 Try and write a proof on why the angles add to 180

The proof StatementReason EC is a lineGiven AB is parallel to ECGiven 1+2+3=180def of a line 1=4AI 3=5AI 4+2+5=180Substitution

Properties of Angles Remember all the different angle properties 1.Vertical 2.Linear Pair 3.AI 4.AE 5.Corr 6.SSI

Isosceles Triangles 1.2 congruent sides - legs 2.2 congruent angles – formed by non congruent sides, base angles 3.Non Congruent side is called the base 4.Vertex – non congruent angle, formed by congruent sides

If legs are congruent then it is an isosceles triangle If base angles are congruent then it is an isosceles triangle

Examples Find the missing measures

Homework Pg Pg Honors pg