Which trigonometric function is defined as hypotenuse/opposite?

The correct definition of the trigonometric function that is calculated as hypotenuse divided by opposite is the cosecant. The cosecant function is actually the reciprocal of the sine function. While sine itself is defined as opposite over hypotenuse, cosecant takes this relationship and flips it. Therefore, if you consider a right triangle, the sine of an angle is the length of the side opposite the angle divided by the hypotenuse. On the other hand, cosecant, being its reciprocal, is calculated by taking the hypotenuse and dividing it by the length of the opposite side.

The other functions mentioned each correspond to different ratios in a right triangle. Sine is specifically opposite over hypotenuse, tangent is opposite over adjacent, and secant is hypotenuse over adjacent. It's essential to remember how these functions relate to one another to clearly understand their definitions and applications in trigonometry.