## Right Triangle

OK, let's see what this is all about.

Firstly, the names **Opposite, Adjacent and Hypotenuse** come from the right triangle:

- "Opposite" is opposite to the angle θ
- "Adjacent" is adjacent (next to) to the angle θ
- "Hypotenuse" is the long one

## Sine, Cosine and Tangent

And **Sine**, **Cosine** and **Tangent** are the three main functions in trigonometry.

They are often shortened to **sin**, **cos** and **tan**.

The calculation is simply **one side of a right angled triangle divided by another side** ... we just have to know which sides, and that is where "sohcahtoa" helps.

For a triangle with an angle ** θ** , the functions are calculated this way:

Sine Function: | soh... | sin(θ) = opposite / hypotenuse |

Cosine Function: | ...cah... | cos(θ) = adjacent / hypotenuse |

Tangent Function: | ...toa | tan(θ) = opposite / adjacent |

## How to Remember

Well, "sohcahtoa" may be easy for you to remember ... but here's another way to help it:

**S**ailors **O**ften **H**ave **C**urly **A**uburn **H**air **T**ill **O**ld **A**ge.

Or perhaps you prefer one of these:

**S**ome**O**ld**H**orses**C**an**A**lways**H**ear**T**heir**O**wners**A**pproach.**S**ome**O**ld**H**en**C**aught**A**nother**H**en**T**aking**O**ne**A**way.

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