you can also remember it in another way, this is my way, it may or may not be useful :p. but first some snazzy ASCII of a triangle.
B
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A ___________|C
Tan = opposite / adjacant:
if you take tan for some degree(or radian for that matter), then you get zhe....zhe......i'll just call i "a"-value for a straight line, you know: y = ax + b.
you can also calculate this a value by divided the change in the y-values with the change in the x-values. say we could take Tan(A) from our snazzy drawing, then we get the change in y-values divided by the change x-values, being |BC| / |AC|. opposite over adjacant.
Sin = Opposite / hypotenuse and Cos = Adjacant / hypotenuse:
i just remember this by the definition of Sine, it spits out the Y-value of the point where the radius touches the circles edge. This is also how i remember cos, since it spits out the x-value.