Isosceles Trapezoid

Definition of Isosceles Trapezoid

    A trapezoid in which non-parallel sides and base angles are equal is called as an Isosceles Trapezoid.

More About Isosceles Trapezoid

  • The diagonals of an isosceles trapezoid are equal.
  • Area of isosceles trapezoid is given by Isosceles Trapezoid, where s1 and s2 are the lengths of the parallel sides and h is the distance (height) between the parallel sides.

Video Examples: Trapezoids : How to Solve an Isosceles Trapezoid


Example of Isosceles Trapezoid

       example of     Isosceles Trapezoid
    The given figure shows the sides AC and BD as equal. Also the base angles ?C and ?D, ?A and ?B are equal. So, it is an isosceles trapezoid.

Solved Example on Isosceles Trapezoid

Ques: Find the measures of angle A, B, and D in the isosceles trapezoid.
     example of     Isosceles Trapezoid

    Choices:
    A. A = 45, B = 135, D = 90
    B. A = 135, B = 135, D = 45
    C. A = 135, B = 90, D = 135
    D. A = 135, B = 135, D = 90
    Correct Answer: B

Solution:

    Step 1: ?C = ?D = 45 [ABCD is an isosceles trapezoid.]
    Step 2: As ?C and ?A are consecutive interior angles formed by parallel lines, they are supplementary. ?A + ?C = 180. [AB || CD, AC transversal.] Step 3: ?A = 180 - 45 = 135 [Solve for A.]
    Step 4: ?B = ?A = 135 [ABCD is an isosceles trapezoid.]