Isosceles Trapezoid- Formula, Definition With Examples

Welcome to another exciting exploration of the wonderful world of geometry with Brighterly! This time, we’re delving into a captivating quadrilateral – the isosceles trapezoid. This unique shape opens the door to a whole new way of understanding mathematical principles. To simply define it, an isosceles trapezoid is a quadrilateral, with two of its sides parallel (the bases), and the other two sides (the legs) are non-parallel but equal in length.

Picture this: you’re enjoying a beautiful day at the park, flying a brightly colored kite. As you watch it dance in the sky, you realize that it resembles an isosceles trapezoid with its two parallel sides, and two non-parallel sides of the same length. You see, geometry is all around us!

What is an Isosceles Trapezoid?

To truly understand the beauty of geometry, one must delve into its various shapes and forms, and a perfect place to start is with the intriguing figure known as the isosceles trapezoid. In simple terms, an isosceles trapezoid is a quadrilateral (a shape with four sides), but what makes it special is that two of its sides are parallel and the other two sides, which are non-parallel, are equal in length.

Imagine this: You’re flying a kite on a warm sunny day. As you look up, you notice the kite’s shape: two sides running parallel to each other, the other two sides of equal length but not parallel. There, floating in the blue sky, is your very own example of an isosceles trapezoid!

Definition of a Trapezoid

Before we dive deeper into isosceles trapezoids, let’s first understand the basic definition of a trapezoid. A trapezoid is a type of quadrilateral, but it has a unique feature: one pair of its sides are parallel. Picture a sloping hillside — the ground and the horizon form two parallel lines, while the sloping sides of the hill are non-parallel. That hillside? It’s a trapezoid!

Definition of an Isosceles Trapezoid

Now, let’s add a little more detail to our trapezoid and turn it into an isosceles trapezoid. What differentiates an isosceles trapezoid from a regular trapezoid is that the non-parallel sides are of equal length. Remember our kite from earlier? Its non-parallel sides are the same length, making it a perfect example of an isosceles trapezoid!

Properties of Trapezoids and Isosceles Trapezoids

Properties of Trapezoids

Trapezoids are fascinating! They have several distinct properties, including the following:

  1. They have one pair of parallel sides (the “bases”).
  2. They have one pair of non-parallel sides.
  3. The parallel sides can be of different lengths.

Properties of Isosceles Trapezoids

Isosceles trapezoids take the intrigue a step further with their unique properties:

  1. They have one pair of parallel sides of unequal length.
  2. The non-parallel sides are of equal length.
  3. The angles adjacent to the base are equal.

Difference Between Trapezoids and Isosceles Trapezoids

While trapezoids and isosceles trapezoids share some properties, there are key differences that set them apart. In a standard trapezoid, the sides that aren’t parallel can be any length. However, in an isosceles trapezoid, these sides must be of equal length. Also, while any two adjacent angles in a trapezoid are supplementary, an isosceles trapezoid’s base angles are always equal.

Geometry Trapezoid Worksheet Answers PDF

View pdf

Geometry Trapezoid Worksheet Answers

Trapezoid Worksheet PDF

View pdf

Trapezoid Worksheet

At Brighterly, we believe that practice is the key to mastery. That’s why we invite you to explore our isosceles trapezoids worksheets, where you can find an array of additional practice questions, complete with answers.

Formulas Related to Isosceles Trapezoids

Writing Formulas of Trapezoids

Formulas are the keys to unlocking the secrets of shapes. The basic formula to find the area of a trapezoid is Area = 1/2(a+b)h, where ‘a’ and ‘b’ are the lengths of the parallel sides, and ‘h’ is the height.

Writing Formulas of Isosceles Trapezoids

For isosceles trapezoids, we can calculate other features like the length of the diagonals or the base angles. The length of the diagonals (d) can be found with the formula d = √(a^2+b^2+2c^2), where ‘a’ and ‘b’ are the bases, and ‘c’ is the leg. Here’s a handy guide for more about these formulas.

Practice Problems on Isosceles Trapezoids

Now that you have a handle on the theory, it’s time for some hands-on practice to strengthen your understanding. Let’s explore some practical examples and interactive problems!

Example 1: Consider an isosceles trapezoid with bases of lengths 10 cm and 20 cm, and a height of 12 cm. Find the area of the trapezoid.

Solution: Recall the formula for the area of a trapezoid: Area = 1/2(a+b)h. Substituting the given values, we find that the area is 1/2(10+20)12 = 180 cm².

Example 2: You have an isosceles trapezoid with equal sides (legs) of length 13 cm, a shorter base of 5 cm, and a longer base of 12 cm. Can you find the height?

Solution: We can use the Pythagorean theorem to solve this. The height will be √(13² - ((12-5)/2)²) = √(169 - 49) = √120 cm.

Interactive Problem: Visit this interactive geometry platform and play around with the dimensions of the trapezoid. Adjust the side lengths, angles, and height, and see how the area and other properties change!

By working through these problems, you’ll get a better understanding of the properties of isosceles trapezoids. You’re well on your way to becoming a geometry whiz!

Trapezoids Worksheet

Trapezoids Worksheet

Trapezoid Geometry Worksheet

Trapezoid Geometry Worksheet


As we wrap up this geometric journey, we hope that we’ve shed some light on the intriguing world of isosceles trapezoids and how they distinguish themselves in the realm of quadrilaterals. At Brighterly, we believe that understanding the fundamental principles of shapes like trapezoids and isosceles trapezoids provide an important stepping stone in the broader understanding of geometry and mathematics as a whole. So, the next time you fly a kite, you’ll look at it with a new perspective, seeing not just a toy dancing in the wind, but a real-life example of the fascinating isosceles trapezoid!

Frequently Asked Questions on Isosceles Trapezoids

What distinguishes an isosceles trapezoid from a regular trapezoid?

The key difference lies in the lengths of the non-parallel sides. In an isosceles trapezoid, these sides are equal in length, whereas in a regular trapezoid, they can be of any length. Also, in an isosceles trapezoid, the base angles are always equal.

How do you calculate the area of an isosceles trapezoid?

The formula for calculating the area of an isosceles trapezoid is Area = 1/2(a+b)h, where ‘a’ and ‘b’ are the lengths of the parallel sides (bases), and ‘h’ is the height.

How can you calculate the height of an isosceles trapezoid?

If you know the lengths of the bases and the legs, you can use the Pythagorean theorem to calculate the height. This would involve subtracting half the square of the difference of the base lengths from the square of the leg length, and then taking the square root.

Through these FAQs, we hope to address the most common queries that might arise in your exploration of isosceles trapezoids. As always, Brighterly is here to make your mathematical journey enlightening and enjoyable!

Information Sources
  1. Wikipedia – Isosceles Trapezoid
  2. National Center for Education Statistics – Isosceles Trapezoids
  3. Wolfram MathWorld – Isosceles Trapezoid

Math Catch Up Program

Image -Math Catch Up Program
  • Learn Math Simple - Fast - Effective
  • Overcome math obstacles and reach new heights with Brighterly.

Kid’s grade

  • Grade 1
  • Grade 2
  • Grade 3
  • Grade 4
  • Grade 5
  • Grade 6
  • Grade 7
  • Grade 8

Simple - Fast - Effective
Overcome math obstacles and reach new heights with Brighterly.

Select Your Grade
Table of Contents

Kid’s grade

  • Grade 1
  • Grade 2
  • Grade 3
  • Grade 4
  • Grade 5
  • Grade 6
  • Grade 7
  • Grade 8
Image full form