sin A = a/c
cos A = b/c
tan A = a/b
similarly:
sin B = b/c
cos B = a/c
tan B = b/a
You can remember this with " SOH CAH TOA. "
Sine of an angle = length of leg Opposite that angle divided by the length of the Hypotenuse
Sin = Opposite / Hypotenuse
Cosine of an angle = length of leg Adjacent that angle divided by the length of the Hypotenuse
Cosine = Adjacent / Hypotenuse
Tangent of an angle = length of led Opposite that angle / length of leg Adjacent that angle
Tangent = Opposite / Adjacent
Remember this only works on right triangles! And the "adjacent" leg cannot be the hypotenuse.