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### Course: Trigonometry > Unit 1

Lesson 2: Introduction to the trigonometric ratios# Trigonometric ratios in right triangles

Learn how to find the sine, cosine, and tangent of angles in right triangles.

The ratios of the sides of a right triangle are called trigonometric ratios. Three common trigonometric ratios are the $A$ below:

**sine (sin)**,**cosine (cos)**, and**tangent (tan)**. These are defined for acute angleIn these definitions, the terms opposite, adjacent, and hypotenuse refer to the

*lengths*of the sides.## SOH-CAH-TOA: an easy way to remember trig ratios

The word

**sohcahtoa**helps us remember the definitions of sine, cosine, and tangent. Here's how it works:Acronym Part | Verbal Description | Mathematical Definition |
---|---|---|

For example, if we want to recall the definition of the $S{O}{H}$ , since ${\text{O}}$ and the ${\text{H}}$ help us to remember that sine is ${\text{opposite}}$ over ${\text{hypotenuse}}$ !

*sine*, we reference*sine*starts with the letter S. The## Example

Suppose we wanted to find $\mathrm{sin}(A)$ in $\mathrm{\u25b3}ABC$ given below:

Sine is defined as the ratio of the ${\text{opposite}}$ to the ${\text{hypotenuse}}$ $(S{O}{H})$ . Therefore:

Here's another example in which Sal walks through a similar problem:

## Practice

**Triangle 1:**$\mathrm{\u25b3}DEF$

**Triangle 2:**$\mathrm{\u25b3}GHI$

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