I'm going to assume that word is "opposite". That being said, the opposite of defeat is, in fact, victory.
...white...
mountless
Dirty....
goose
Abundant
bright
a scottish word for boy
a line.
immigration
Uh... Weak? What is the point in this question?
Defeat is a noun (a defeat) and a verb (to defeat).
You have not described this problem in sufficient detail. If you are talking about triangles, then in some situations trigonometric functions are applicable. Or, you could just measure the side with your ruler, although if that is what you are going to do, then the fact that it is oppoiste an angle is irrelevant.