+118608 Cos is short for cosine
Think about a right angled triangle. It has a right angle and 2 acute angles. The acute angles add up to 90 degrees.
so the angles could be $$90^0, A\:\: and \:\: (90-A)$$
We are think in about the $$A$$ angle.
You label the hypotenuse - it is the longest side
Cos $$A$$ = adjacent side / hypotenuse
For any given angle this ratio always stays the same.
I would draw a more appropriate picture but there is a problem with inserting attachments at the moment. 
+118608 Cos is short for cosine
Think about a right angled triangle. It has a right angle and 2 acute angles. The acute angles add up to 90 degrees.
so the angles could be $$90^0, A\:\: and \:\: (90-A)$$
We are think in about the $$A$$ angle.
You label the hypotenuse - it is the longest side
Cos $$A$$ = adjacent side / hypotenuse
For any given angle this ratio always stays the same.
I would draw a more appropriate picture but there is a problem with inserting attachments at the moment.
