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Lesson 3-2

Isosceles Triangles. Lesson 3-2. 3. Leg. Leg. Ð. 1 and . Ð. 2 are base angles. Ð. 3 is the vertex angle. 1. 2. Base. Parts of an Isosceles Triangle. An isosceles triangle is a triangle with two congruent sides.

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Lesson 3-2

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  1. Isosceles Triangles Lesson 3-2 Lesson 3-2: Isosceles Triangle

  2. 3 Leg Leg Ð 1 and Ð 2 are base angles Ð 3 is the vertex angle 1 2 Base Parts of an Isosceles Triangle • An isosceles triangle is a triangle with two congruent sides. • The congruent sides are called legs and the third side is called the base. Lesson 3-2: Isosceles Triangle

  3. A B C ° 50 ° x Isosceles Triangle Theorems If two sides of a triangle are congruent, then the angles opposite those sides are congruent. Example: Find the value of x. By the Isosceles Triangle Theorem, the third angle must also be x. Therefore, x + x + 50 = 180 2x + 50 = 180 2x = 130 x = 65 Lesson 3-2: Isosceles Triangle

  4. A B C A 3x - 7 x+15 ° ° B 50 50 C Isosceles Triangle Theorems If two angles of a triangle are congruent, then the sides opposite those angles are congruent. Example: Find the value of x. Since two angles are congruent, the sides opposite these angles must be congruent. 3x – 7 = x + 15 2x = 22 X = 11 Lesson 3-2: Isosceles Triangle

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