Angle Bisector – Definition, Properties, Construction

Geometry, a fascinating world filled with shapes, lines, and angles, is an adventure waiting to be embarked upon. At Brighterly, we aim to be your guiding star in this journey, illuminating every corner of the geometric universe. Today, we’ll spotlight the intriguing concept of the Angle Bisector. An integral part of this universe, the angle bisector might seem like a simple line dividing an angle, but there’s much more to it. In this article, we’ll navigate through the captivating waters of what an angle bisector is, its unique properties, and the craft of its construction. So, put on your explorer hat, grab your compass (the geometric one, of course!), and let’s embark on this exciting adventure with Brighterly!

What is an Angle Bisector?

Imagine you’re on a journey through the geometric universe, and you come across a unique celestial body – an angle. An angle, much like a slice of pizza, is a piece of a larger whole. Now, if you’re a fair-minded explorer (and if you’re here with Brighterly, we’re sure you are!), you’d want to divide that slice evenly to share. This is where an angle bisector comes into play. An angle bisector is a line or ray, like a beam of starlight, that slices an angle into two identical or congruent parts. So, with an angle bisector, you’ve created two equal angles, much like having two equally delicious pieces of cosmic pizza!

Angle Bisector of a Triangle

Venturing further into our geometric cosmos, let’s enter the realm of triangles. In a triangle, an angle bisector is akin to a cosmic bridge. It starts at one angle and extends, bisecting that angle, to reach the opposite side of the triangle. The magic of this journey is that it maintains a perfect balance. The bisector will always divide the opposite side in the same proportion as the lengths of the two sides forming the angle it bisects. Suppose we have a triangle named ABC, where AD is the angle bisector of ∠A. Then, in the cosmic balance of geometry, the ratio of AB to AC will be equal to the ratio of BD to DC. 

Properties of an Angle Bisector

Much like a star having unique properties that define its identity in the vast universe, an angle bisector has its distinct characteristics. Here are some of them:

  1. It divides a given angle into two congruent angles, maintaining a cosmic balance.
  2. Within a triangle, an angle bisector births two new triangles, both of which are similar to the original triangle and each other, creating a beautiful pattern of similarity.
  3. In a triangle, the angle bisector intersects the opposite side in the same ratio as the lengths of the adjacent sides, maintaining a constant proportion.

Construction of Angle Bisector

The ability to construct an angle bisector is like having a cosmic compass and straightedge. This process might seem like a magic trick, but it’s all about understanding the steps and practicing. Let’s learn how to create this geometric magic.

How to Construct an Angle Bisector?

  1. Draw an angle: Let’s start our cosmic construction by sketching an angle using a straightedge.
  2. Draw an arc: With the vertex of your angle as the epicenter, draw an arc that cuts through both rays of the angle.
  3. Draw two more arcs: Hold your compass steady, and draw two more arcs, each centered on where your first arc intersects the rays of the angle.
  4. Draw the bisector: Finally, draw a ray from the vertex of the angle through the point where the two smaller arcs intersect. There you have it! You’ve successfully constructed your angle bisector!

Angle Bisector Theorem

Just as the laws of physics govern the cosmos, the Angle Bisector Theorem is a fundamental principle in the universe of geometry. This theorem states that the ratio of the lengths of the two segments created by the bisector on the opposite side equals.


And thus, we conclude our voyage through the realm of angle bisectors. With Brighterly as your guiding light, you’ve traversed the intricate landscape of this vital geometric concept, unearthed its unique properties, and mastered the art of its construction. Remember, the world of geometry, much like our universe, is vast and filled with wonders. An angle bisector is more than a mere line splitting an angle into two congruent parts; it’s a key that unlocks the door to a myriad of geometric phenomena, particularly within the context of triangles.

But our journey doesn’t end here. In the realm of mathematics, every conclusion is but the beginning of a new adventure. With the knowledge you’ve acquired today, you’re equipped to face more complex challenges and uncover deeper mysteries. So, keep that explorer spirit alive, continue practicing, and let your curiosity guide you. With Brighterly by your side, you’re not just learning math, you’re embracing the thrill of discovery, one concept at a time. Until our next adventure, keep exploring, keep learning, and most importantly, keep shining brightly with Brighterly!

Frequently Asked Questions on Angle Bisectors

What is an angle bisector?

An angle bisector is a line or ray that divides an angle into two equal, or congruent, parts. In other words, if you have an angle, an angle bisector would split that angle into two smaller angles, each of which would be half the size of the original. This is a fundamental concept in geometry and has various applications in solving mathematical problems.

How do I construct an angle bisector?

Constructing an angle bisector can be accomplished using a compass and a straightedge. The process involves creating an arc that intersects the rays of the angle, then using the intersections to draw additional arcs, and finally drawing a ray from the angle’s vertex through the intersection of the last two arcs. This ray is your angle bisector, splitting the original angle into two congruent angles.

What are the properties of an angle bisector?

The properties of an angle bisector are quite interesting. For one, it divides an angle into two equal parts. In the context of a triangle, an angle bisector creates two similar triangles, meaning the corresponding sides are proportional, and the corresponding angles are equal. Furthermore, in a triangle, the ratio of the lengths of the two segments created by the bisector on the opposite side is equal to the ratio of the lengths of the other two sides.

What is the Angle Bisector Theorem?

The Angle Bisector Theorem is a principle in geometry that states an angle bisector in a triangle divides the opposite side into two segments that have the same ratio as the other two sides of the triangle. It’s an essential tool in geometry, assisting in the solution of various problems, such as finding unknown lengths or angles in a triangle.

Additional Sources of Information
  1. Wikipedia
  2. MathBitsNotebook
  3. Math Open Reference

Remember, understanding mathematical concepts is more important than memorizing them. Continue to explore, learn, and enjoy mathematics with Brighterly! Happy learning!

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