CDEF is an isosceles trapezoid and
What do you know about the angles of an isosceles trapezoid?
You know that each pair of base angles is congruent. Because the bases of a trapezoid are parallel, you also know that two angles that share a leg are supplementary.
Since each pair of base angles of an isosceles trapezoid is congruent,
Paper Fans The second ring of the paper fan shown below consists of 20 congruent isosceles trapezoids that appear to form circles. What are the measures of the base angles of these trapezoids?
Step 1 Find the measure of each angle at the center of the fan. This is the measure of the vertex angle of an isosceles triangle.
What do you notice about the diagram?
Each trapezoid is part of an isosceles triangle with base angles that are the acute base angles of the trapezoid.
Step 2 Find the measure of each acute base angle of an isosceles triangle.
Step 3 Find the measure of each obtuse base angle of the isosceles trapezoid.
Each acute base angle measures 81. Each obtuse base angle measures 99.