Which is NOT an example of the three trigonometric reciprocals of sine, cosine and tangent?

The three reciprocal trigonometric functions are cosecant (the reciprocal of sine), secant (the reciprocal of cosine), and cotangent (the reciprocal of tangent). A theorem is a mathematical statement that can be proved, not a trigonometric reciprocal, so the correct choice is theorem.

AI-written and checked against the verified answer.