Unit 4 Lesson 1 CLASSIFYING TRIANGLES

 I will be able to classify triangles according to the angle measures and side lengths.  I WILL be able to define basic parts of triangles.  I will be able to find the third angle in a triangle?  I WILL be ABLE to USE the EXTERIOR angle THEOREM to FIND missing MEASUREMENTS.  I will recognize congruent triangles by identifying corresponding parts!  I will be able to use the congruence of figures to find missing measurements. #imawesome #Ilovemath #yesijustsaidilovemath LEARNING OUTCOMES

 A triangle is a figure formed by three segments joining three noncollinear points.  Each of the three points joining the sides of a triangle is a vertex. VOCABULARY AB C Notation Alert!!! To name this triangle, we use this notation: ABC (the letters can be arranged in any order)

 Cut your pieces of card stock into five different lengths. A 2- inch piece, 3-inch piece, 4-inch piece, 5-inch piece and 6 inch piece.  Label the different pieces.  On a separate sheet of paper create two columns. One labeled “Pieces that make a triangle” the other labeled “Pieces that don’t make a triangle”  Use the pieces that you cut earlier to form as many triangles as possible. Keep track of the pieces that can form a triangle and the pieces that can’t form a triangle. What do you notice about the pieces that do form a triangle and the pieces that don’t form a triangle? WHAT MAKES A TRIANGLE?

 To put that into words: WHAT MAKES A TRIANGLE?

 2,3,6  4, 10, 12  16, 21, 37  35, 36, 70 CAN THESE SEGMENTS FORM A TRIANGLE?

 2, 8, x  14, 20, x  30, 41, x WHAT CAN YOU DETERMINE ABOUT THE THIRD SIDE?

CLASSIFICATION BY SIDES

CLASSIFICATION BY ANGLES When classifying triangles, you must classify by both sides and angles!!!

 In an isosceles triangle, the two congruent sides are the legs of the isosceles triangle.  In an isosceles triangle with two congruent sides, the third side is the base. (It’s the one that is not congruent to any other!) ISOSCELES TRIANGLES

 In a right triangle, the sides that form the right angle are the legs of the right triangle.  The side opposite the right angle is the hypotenuse of the triangle. RIGHT TRIANGLES

 In a triangle, two sides sharing a common vertex are adjacent sides.  When the sides of a triangle are extended, the interior angles are the three original angles.  When the sides of a triangle are extended, the exterior angles are the three angles adjacent to the interior angles. VOCABULARY

TRIANGLE SUM THEOREM

 A corollary to a theorem is a statement that can be proved easily using the theorem. VOCABULARY Since the sum of the interior angles has to be 180 and one angle is 90, the other two have to be 90 together!!

EXTERIOR ANGLES THEOREM

CAN YOU PROVE IT? THINK-PAIR-SHARE

 Sides?  Angles? WHAT MAKES FIGURES CONGRUENT?

CONGRUENT FIGURES

YOUR TURN

 Copy these problems onto the paper you will turn in:  4.1)  4.2) LET’S START YOUR HOMEWORK! HW: Pg. 198: 16-26, , Pg. 206: 16-21,