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124_G6U25_WB_˙—» ¿º 2011.6.23 3:32 PM ˘ ` 17
124-P2-1
Isosceles Triangles and Angles
Triangle ABC is an isosceles triangle and BC DE. Find the unknown
angle. A
40
D E
a C
B
Step 1. What is the sum of the interior angles of a triangle?
Step 2. In an isosceles triangle, the two interior angles are congruent.
Find m ABC and m ACB.
Step 3. Find m ADE.
Step 4. Find m a.
124-P2-1
Isosceles Triangles and Angles
Triangle ABC is an isosceles triangle and BC DE. Find the unknown
angle. A
40
D E
a C
B
Step 1. What is the sum of the interior angles of a triangle?
Step 2. In an isosceles triangle, the two interior angles are congruent.
Find m ABC and m ACB.
Step 3. Find m ADE.
Step 4. Find m a.
