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Unit 4 Lesson 6 Notes Use Isosceles and Equilateral Triangles. Parts of an Isosceles Triangle. leg. leg. base. Angles opposite the congruent sides. Angle between the congruent sides. Side not congruent. Sides congruent. Base Angles Theorem:
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Unit 4 Lesson 6 NotesUse Isosceles and Equilateral Triangles
Parts of an Isosceles Triangle leg leg base Angles opposite the congruent sides Angle between the congruent sides Side not congruent Sides congruent
Base Angles Theorem: • If two sides of a triangle are ___________, then • the ________ ____________ the sides are • ____________. congruent angles opposite congruent
Theorem (converse of the Base Angles Theorem): • If two angles of a triangle are congruent, then the sidesopposite the angles are congruent.
40° 6 6 a b 1. Find the missing angles. 70° 180 – 40 2 a = = 70° b = 70°
1. Find the missing angles. 30° a = 120° 180 – 30 – 30 = b = 30°
1. Find the missing angles. 180 3 = 60° 60° 60° 60°
1. Find the missing angles. 90 2 = 45° a 45° 45° b
2. Find the missing variables. 45° 45° y + 7 = 45 3x = 45 x = 15 y = 38
2. Find the missing variables. 3x – 11 = 2x + 11 x – 11 = 11 x = 22° 55° 55° 55° 3(22) – 11 = 2y + 55 + 55 = 180 2y + 110 = 180 2y = 70 y = 35°
2. Find the missing variables. 32° 32° 58° 58°
2. Find the missing variables. 65° 25° 130° 50° 25° 65°
3. Find the perimeter of the triangle. 2x – 1 = x + 4 9ft x – 1 = 4 9ft x = 5 P = 9 + 9 + 7 P = 25ft
3. Find the perimeter of the triangle. 10x – 32 = 5x – 7 18in 5x – 32 = –7 5x = 25 x = 5 P = 18+18+14 P = 50in 18in
3. Find the perimeter of the triangle. 3x – 1 = x + 13 20ft 20ft 2x – 1 = 13 2x = 14 x = 7 20ft P = 20+20+20 P = 60ft
HW Problem # 16 x + 7 = 55 55 x = 48° y + 55 + 55 = 180 y + 110 = 180 y = 70°