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Distance Between Two Points – Definition with Examples

Jo-ann Caballes

Updated on January 3, 2024

Have you ever thought about the distance that a bird covers when it flies straight from a tree to the ground, or the path a spaceship takes when it moves from one point to another in the cosmos? All these scenarios involve the concept of distance between two points. In the colorful world of mathematics, and specifically in geometry, the term ‘distance’ refers to the length of the shortest line connecting two distinct points. In essence, it’s like imagining an invisible thread stretched tightly between two points—this thread represents the distance. At Brighterly, we believe that a deep understanding of such fundamental mathematical concepts can unlock a universe of problem-solving skills and creative thinking in children. So, let’s dive in together and explore the notion of distance in more depth, journeying through its formula, derivation, and examples that you can use to practice at home or in the classroom!

What is the Distance Between Two Points?

The concept of distance is a fundamental one in our everyday lives. Whether we’re traveling to school, planning a vacation, or playing a video game, we often need to know the distance between two points. In mathematics, particularly in geometry, the term ‘distance’ refers to the length of the straight line connecting two points. For instance, imagine an ant crawling from one point to another. The shortest path it would take represents the distance between those two points. Interestingly, this concept also extends beyond our three-dimensional world and applies to the abstract spaces of mathematics and physics. To make this concept more concrete, we’ll delve into its numerical representation and explore the widely used distance formula.

Distance Between Two Points Formula

In a two-dimensional space, such as a graph or map, we can find the distance between two points using a mathematical formula derived from the famous Pythagoras’ theorem. Let’s consider two points in a plane, say, A(x₁, y₁) and B(x₂, y₂). The distance (d) between these two points can be calculated using the formula:

d = √[(x₂ – x₁)² + (y₂ – y₁)²]

This formula essentially measures the length of the line segment connecting points A and B. Don’t be intimidated by its mathematical notation; we will dissect it piece by piece and demonstrate how to use it effectively.

Derivation of Formula for Distance Between Two Points of Coordinates

Wondering where the formula came from? It is not just a random equation but a derivation based on the principles of the Pythagorean theorem. Let’s delve into its derivation:

Consider a two-dimensional plane with points A(x₁, y₁) and B(x₂, y₂). Draw a line segment AB connecting these points. Now, let’s form a right-angled triangle with AB as the hypotenuse, one vertex at A, and the other vertex directly beneath or above B on the x-axis (let’s call this point C).

Since C lies on the x-axis, its coordinates would be (x₂, y₁). Hence, the length of AC is |x₂ – x₁|, and the length of BC is |y₂ – y₁|. Now, using the Pythagorean theorem (which states that in a right-angled triangle, the square of the hypotenuse equals the sum of the squares of the other two sides), we can derive our distance formula.

How to Find Distance Between Two Points of Coordinates?

Once you understand the formula, it becomes a matter of simple calculation. Let’s take an example to make it clear.

Suppose we have two points A(3,4) and B(7,10). To calculate the distance between them:

1. Substitute the coordinates in the distance formula, i.e., d = √[(x₂ – x₁)² + (y₂ – y₁)²].
2. Perform the arithmetic operations to get the answer.

Step-by-step calculations can truly help kids grasp this concept better. For additional help, interactive tools available online can further enhance understanding.

Derivation of Distance Formula

The concept of distance between two points hinges heavily on the historical Pythagorean theorem. This theorem, discovered by the ancient Greek mathematician Pythagoras, revolutionized the way we measure distances and has extensive applications in various fields, from architecture to physics.

To understand the derivation of the distance formula, let’s revisit the Pythagorean theorem. The theorem states that in a right-angled triangle, the square of the hypotenuse (the longest side) equals the sum of the squares of the other two sides.

Consider a two-dimensional plane, and let’s take two points on it, A(x₁, y₁) and B(x₂, y₂). If you draw a line connecting these two points, this line can be considered as the hypotenuse of a right-angled triangle. Let’s call the right angle of this triangle C. Now, C is at the position (x₂, y₁) in the plane.

The length of AC (one of the sides) is the absolute difference between x₂ and x₁, or |x₂ – x₁|. Similarly, the length of BC (the other side) is the absolute difference between y₂ and y₁, or |y₂ – y₁|. According to the Pythagorean theorem, the square of AB (hypotenuse) is the sum of the squares of AC and BC.

So, (AB)² = (AC)² + (BC)², which translates to (AB)² = (x₂ – x₁)² + (y₂ – y₁)². If we take the square root on both sides, we get the formula for distance AB = √[(x₂ – x₁)² + (y₂ – y₁)²].

This formula, derived from the Pythagorean theorem, is a powerful tool in mathematics, allowing us to calculate the distance between any two points in a plane.

Distance of a Point from the Origin

The distance of a point from the origin (0,0) follows the same principle. We simply substitute x₁ and y₁ as zero in our distance formula. Therefore, for a point P(x, y), the distance from the origin O is:

d = √[(x – 0)² + (y – 0)²] = √[x² + y²]

Distance between Two Points: Using Pythagoras’ Theorem

As stated earlier, the distance formula is a direct application of the Pythagorean theorem. The theorem is a pillar of geometry, stating that in a right-angled triangle, the square of the hypotenuse equals the sum of the squares of the other two sides. We essentially create a right-angled triangle between our two points and the x-axis to utilize this theorem for calculating distance.

Practice Questions on Distance Between Two Points

Now that we’ve uncovered the magic behind the distance formula, it’s time to put that knowledge into practice! Just like a basketball player practices shooting hoops or a pianist practices scales, solving problems using the distance formula will help solidify your understanding and improve your skills.

1. Problem 1: What is the distance between the points A(0,0) and B(5,5)?

2. Problem 2: Find the distance between the points C(-2,3) and D(4,-1).

3. Problem 3: What is the distance from the origin to the point E(3,4)?

4. Problem 4: If the distance between point F(a,b) and the origin is √10, and a = 1, what is the value of b?

Conclusion

In this captivating exploration, we journeyed through the intriguing world of geometry and discovered the concept of distance between two points. Along the way, we unraveled the Pythagorean theorem, derived the distance formula, and tested our understanding with practice problems. We’ve seen how this seemingly simple concept forms the bedrock of many aspects of mathematics and the world around us.

At Brighterly, we believe in nurturing curiosity, fostering understanding, and cultivating the joy of learning. We hope that this journey through the distance between two points has not just helped you grasp a mathematical concept, but also inspired a sense of wonder and curiosity about the numbers and shapes that make up our world.

Frequently Asked Questions on Distance Between Two Points

What happens if one or both coordinates of the two points are negative?

When calculating the distance between two points, it’s possible to encounter negative coordinates. This is quite common, especially when dealing with graphs that extend into the negative quadrants. Don’t let negative numbers intimidate you. Just substitute them into the distance formula as they are. The square of a negative number is always positive, and since the distance is a length, it can never be negative.

Can this concept extend beyond two dimensions?

Absolutely! The beauty of mathematics is that many of the principles that apply in two dimensions also extend to three dimensions and beyond. In three-dimensional space, for instance, the distance between two points A(x₁, y₁, z₁) and B(x₂, y₂, z₂) is given by: d = √[(x₂ – x₁)² + (y₂ – y₁)² + (z₂ – z₁)²] As you can see, it’s just a small tweak from the two-dimensional distance formula!

Why is it important to learn about the distance between two points?

The concept of distance finds extensive application in numerous fields, from physics and computer graphics to navigation and architecture. It’s a foundational concept in geometry and trigonometry, helping us understand shapes, space, and sizes. Learning about the distance between two points isn’t just about solving specific mathematical problems; it’s about developing spatial awareness and critical thinking skills.

Jo-ann Caballes

5 articles

As a seasoned educator with a Bachelor’s in Secondary Education and over three years of experience, I specialize in making mathematics accessible to students of all backgrounds through Brighterly. My expertise extends beyond teaching; I blog about innovative educational strategies and have a keen interest in child psychology and curriculum development. My approach is shaped by a belief in practical, real-life application of math, making learning both impactful and enjoyable.