Warm up OBJECTIVE: Students will classify triangles by there sides and angles and find missing angle measurements in triangles right acute obtuse When lines are parallel as indicated, the alt. int.  ’s 

OBJECTIVE: Students will analyze and classify Triangles by sides & angles, prove triangles congruent & use coordinate geometry to investigate triangle relationships. Why? Triangles are used to add strength to structures in real-world situations. For example, the frame of a hang glider involves several triangles. Mastery is 80% or better on Practice Problems and 5- Minute Checks.

Copy those terms for which you are unfamiliar

(3 ways) 023 Skill Development

Think….Ink…Share….Quick Write In your own words compare and contrast isosceles, scalene and equilateral triangles. Hint: How are they similar? Different?

(4 ways) 1313 equiangular  ’s are also equilateral Skill Development

isosceles acute isosceles 72,72,36

Pair Share With a partner discuss the criterion in the following triangles: Acute Right Obtuse Equiangular

x x

 RST is a right  (3--1) (-3-3) (3-5) (-3-5) (3-2) (-1-2) right Skill Development

Two of the most important theorems you ever need

What should we do now? 3x – 9 = x x = 82 x = 41 Guided

2x + x + 90 = 180  sum theorem 3x = 90 x = 30 What kind of triangle is this? Right scalene Guided ……White Boards

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Recall: 8x x (  sum corollary)

How’s this for a challenge? Hint: draw and label a picture ABC Which angle is biggest? Let x = the smallest angle x 2x 3x x + 2x + 3x = 180  sum theorem 6x = 180 x = 30 m  A = 2(30) = 60 m  B = 30 m  C = 3(30) = 90

Don’t be afraid to recognize properties we used last week Notice the parallel lines Y = 30 alt int  ’s  x = 60 corollary to  sum OR x + 30 = 90 ext  theorem x = 60

Find y first y = 90 – 39 = 51 Find this  ? = 180 – (50+51) = 79 x = 180  sum Theorem x = 45 corollary to  sum

Sometimes it “helps” to “separate” the triangles. Label our known values xx 25  20  yy yy 25  Find y y+25 = 90 y = 65 By ∆ sum, this angle is 95  So x = = 85

Exit Slips 1.How many ways can a triangle be classified by its sides? Name them. 2.How many ways can a triangle by classified by its angles? Name them. 3.What do all the angles of any triangle ALWAYS add up to? Name the theorem. 4.Find x and y. (copy picture)

WHAT WAS TODAYS OBJECTIVE ?? STUDENTS WILL ANALYZE TRIANGLES, FIND THEIR MEASURES AND CLASSIFY THEM BY THEIR SIDES AND THEIR ANGLES.

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