Pythagorean Theorem Essentials
Right Triangle Basics
The Anatomy of a Right Triangle
Triangles are one of the most fundamental shapes in geometry. They have three sides and three angles. A special type of triangle, which is the foundation for many ideas in math and engineering, is the right triangle.
A right triangle is simply a triangle that has one angle measuring exactly 90 degrees. This 90-degree angle is called a right angle, and it's often marked with a small square in the corner.
The sides of a right triangle have special names. The two sides that meet to form the 90-degree angle are called the legs. They are perpendicular to each other, like the corner of a square.
The third side, which is always opposite the right angle, is called the hypotenuse. An easy way to spot the hypotenuse is that it's always the longest side of the right triangle.
hypotenuse
noun
The longest side of a right triangle, opposite the right angle.
Angles and Properties
The three angles in any triangle always add up to 180 degrees. In a right triangle, we already know one angle is 90 degrees. That leaves the other 90 degrees to be split between the remaining two angles.
This means that the other two angles in a right triangle must be acute. An acute angle is any angle that measures less than 90 degrees. So, a right triangle always has one right angle and two acute angles.
Recognizing the legs and the hypotenuse is the first step toward understanding many powerful geometric relationships. Let's review these key ideas.
What is the defining characteristic of a right triangle?
In a right triangle, the side opposite the 90-degree angle is called the __________.
Now that you can identify the parts of a right triangle, you're ready to explore its most famous property.