What is the reciprocal function of sin a?

Sin(A) = Opposite/Hypotenuse

Its reciprotcal is

1/Sin(A) = Cosecant(A) = Csc(A) = Hypotenuse / Opposite.

Similarly

Cos(A) = Adjacent/Hypotenuse

Its reciprotcal is

1/Cos(A) = Secant(A) = Sec(A) = Hypotenuse / Adjacent

Tan(A) = Opposite/Adjacent

Its reciprotcal is

1/Tan(A) = Cotangent(A) = Cot(A) = Adjacent / Opposite.