Download Lesson 13-2: Isosceles Triangles

Lesson 13-2: Isosceles Triangles
TSW: DEVELOP THEOREMS ABOUT ISOSCELES TRIANGLES.
TSW: PROVE THEOREMS ABOUT ISOSCELES TRIANGLES.
Lesson 13-2: Isosceles Triangles
Warm-Up
Find the measurement of A.
Find the value of x.
57°
x + 17
x
63°
mA = 20°
x = 120°
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Isosceles Triangle – A triangle
with at least 2 congruent sides
and 2 congruent angles.
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50°
130°
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x = 25
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And the perimeter of the triangle.
Perimeter = 145
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18. AC = 18
19. 30°
20 a. x = 6
b. mA = 20° mB = 30° mC = 130°
c. scalene, obtuse
21. Disagree. Since the sum of the angle
measures in a triangle is 180°, the only
possible value of y is 32°. Since no two
angles of the triangle are congruent, the
triangle cannot be isosceles.