Maybe the top part of this will help.
http://www.mathsisfun.com/sine-cosine-tangent.html
If you know either the hyp. or the side adj. and the angle between them , take the sine of the angle times the hyp. = side opp. or take tangent of angle times side adj. = side opp. you realy dont need to use cosine at all.
Rustynut "jus get n by"
