The trigonometric ratios relate sides of a right angled triangle, in reference to whichever angle is being considered.

The sides forming the rightangle are referred to as being "opposite the angle being considered" or "adjacent to the angle being considered". The third, longest side is called the "hypotenuse". Thes are illustrated in the following diagrams:

If we call the angle , then:

... or ...
... or ...
S=O/H	C=A/H	T=O/A
These are usually memorised as the nonsense word:
SOHCAHTOA
Or as one of many and various nonsense phrases, such as...
Silly Old Hitler Can’t Adjust His Trousers Over Apples.
Sad Oliver Had Cabbage And Hamburger Too Often, Alas!
Some Officers Have Curly Auburn Hair To Obtain Airmen.
Sid’s Old Hairy Cart-horse Arrived. He Trod On Albert.
(Don’t blame me!! I didn’t invent these things – I just report them!)

Most recently updated at 18:32 (British time) on 07 April 2004