CPM Homework Banner

Home > GC > Chapter 5 > Lesson 5.3.4 > Problem 5-105

5-105.
  1. Multiple Choice: In the triangle at right, x must be:Homework Help ✎

    1. 42°

    2. 69°

    3. 21°

    4. 138°

    5. none of these

The triangle is isosceles meaning 2 sides are equal.

The measure of x must be the same as the other unknown angle because base angles are equal in an isosceles triangle.

Since the sum of all the interior angles of a triangle must be 180°, then x + x + 42° = 180°.
So the answer is (b).