Trigonometry
In a right angled triangle, the side opposite the right angle is called the hypotenuse.
If one of the other angles is \(x^\circ\), then we can label the remaining sides as shown in this diagram.
There are 3 trig ratios you need to know:
- sine
- cosine
- tangent
We shorten these to:
- sin
- cos
- tan
The three important ratios are:
\(\sin (x^\circ ) = \frac{{opposite}}{{hypotenuse}}\)
\(\cos (x^\circ ) = \frac{{adjacent}}{{hypotenuse}}\)
\(\tan (x^\circ ) = \frac{{opposite}}{{adjacent}}\)
Some people remember a well-known mnemonic using the first letters to help when deciding which ratio to use for each trig problem.
This mnemonic is:
SOH CAH TOA
These letters stand for:
S sine O opposite H hypotenuse
C cosine A adjacent H hypotenuse
T tangent O opposite A adjacent