Unit 6 (Part II) – Triangle Similarity



Cholkar MCHS MATH II ___/___/___ Name____________________________

|5.1 |How can I prove the sum of the angles of any triangle? |

| |How can I determine if a triangle is an isosceles triangle? |

|HW # | Complete Handout [1, 3, 4] |

|Do Now |Find m[pic] L. |

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{different size triangles/ group, protractors, patty paper}

INVESTIGATION: TRIANGLE SUM THEOREM

My Team role for this investigation:__________________

Do the angle measures of a triangle have anything in common?

Step 1 Measure the three angles of each triangle as accurately as possible with your

protractor

Step 2 Find the sum of the measures of the three angles in each triangle. Compare

results with others in your group. Does everyone get about the same result?

If so, what is it?

Step 3 Check the sum another way. Write the letters a, b, and c in the interiors of the

three angles of one of the triangles.

Step 4 Tear off the three angles like shown to the right.

Step 5 Arrange the three angles so that their vertices meet at a point. How does this

arrangement show the sum of the angle measures? Compare your results with

others in your group. Complete the Theorem below.

|TRIANGLE SUM THEOREM: |

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[pic]

a. _______________________________________________________________________________________

b. _______________________________________________________________________________________

c. _______________________________________________________________________________________

d. _______________________________________________________________________________________

5.1 MVP Book Experiment # 2

INVESTIGATION Base Angles of an Isosceles Triangle

Let’s examine the angles of an isosceles triangle. Each person in your group should draw a different angle using your straightedge. Your group should have at least one acute angle and one obtuse angle.

[pic]

|ISOSCELES TRIANGLE THEOREM: If a triangle is isosceles, then |

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[pic]

b. _______________________________________________________________________________________

c. _______________________________________________________________________________________

Corresponding angles: _____________________________________________________________________

GROUP PRACTICE

Find the value of x.

1. 2. 3.

4. Find the measure of the numbered angles.

Find the value of x and y.

|a. |b. |

|c. |d. |

|Lesson Summary |Describe properties of an isosceles triangle that you know by definition or by reasoning. |

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Math Toolkit Vocabulary Entry: triangle sum theorem, base angles, isosceles triangle theorem, corresponding angles (vertices)

Cholkar MCHS MATH II ___/___/___ Name____________________________

HW #

1. Find the missing angle measures in the triangle.

a. b. c.

d.

2.

3.

4.

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