# How to Calculate Angles on a Right Triangle

A right triangle is a special type of triangle that has one angle measuring 90 degrees. In this article, we will look at how to calculate the other two angles of a right triangle using trigonometry and the Pythagorean theorem.

To get started, let’s first understand the various parts of a right triangle:

**1. Hypotenuse** – The longest side of the right triangle (opposite the right angle)

**2. Adjacent** – The side that forms an angle with the hypotenuse

**3. Opposite** – The side that is across from the angle in question

Now that we know these terms, we can learn how to calculate angles in a right triangle using trigonometric ratios and inverse trigonometric functions.

**Trigonometric Ratios:**

**1. Sine (sin)** – Opposite/Hypotenuse

**2. Cosine (cos)** – Adjacent/Hypotenuse

**3. Tangent (tan)** – Opposite/Adjacent

To find an angle using trigonometry, you will need to use inverse trigonometric functions:

**1. Arcsine (asin)** – If you know the opposite and hypotenuse

**2. Arccosine (acos)** – If you know the adjacent and hypotenuse

**3. Arctangent (atan) **– If you know the opposite and adjacent sides

**Here’s how to apply these concepts:**

Step 1: Find out which sides of the triangle you have measurements for.

Step 2: Choose an appropriate trigonometric ratio based on the given side lengths.

Step 3: Use an inverse trigonometric function to find the angle corresponding to the chosen ratio.

For example, let’s say we have a right triangle with an opposite side length of 3 units and an adjacent side length of 4 units.

Step 1: We have measurements for the opposite (3) and adjacent (4) sides.

Step 2: With the measurements, we can use the tangent ratio: tan(θ) = Opposite/Adjacent

Step 3: Applying the arctangent function, we get θ = atan(3/4). Solving for θ, we find that the angle is approximately 36.87 degrees.

Since a triangle has a total sum of 180 degrees and we already know one of the angles is 90 degrees (right angle), we can easily find the third angle by subtracting the two known angles from 180 degrees:

Third angle = 180 – 90 – 36.87 ≈ 53.13 degrees

In conclusion, by using trigonometric ratios and inverse trigonometric functions, you can calculate the angles in a right triangle when given side lengths. Having a strong understanding of right triangles will definitely help you in various mathematical, scientific, and engineering applications.