**In this module, you can study ****how to use trig ratios (sine, cosine and tangent) to find an unknown side length in a right triangle.**

** **

To find the **unknown side length**, you have to use sine, cosine or tangent.

The buttons on your calculator are: **sin** **cos** **tan**

A **'TOA'** example from the second video:

- Unknown
**O**pposite side of a triangle **A**djacent side of 40m- Angle of 24

On a calculator, type: **40 X **** tan ( 24 ) =**

The answer you should get is: **17.8 m**

**Study and practice**

- Study using trig ratios to find the length of a sideThis page from mathsisfun.com explains how to choose which trig ratio (sine, cosine or tangent) to use when you need to find the length of a side. There is also a set of interactive practice problems at the bottom of the page.
- Quiz yourself on finding an unknown side length using trigDo you know how to find an unknown side length using sine, cosine and tangent? Check your understanding with this online quiz at mathopolis.com

The video above explains how to use basic trig functions on a Casio fx-991 calculator.

0.44 min - setting up 'degree' mode

1.19 min - find an unknown side length

- Online scientific calculator from Calculator.netTo open the scientific calculator in a new window, you MUST click the link.

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