Cambridge IGCSE Additional Mathematics · Syllabus 0606 · Trigonometry
Reciprocal Trigonometric Functions
What is Reciprocal Trigonometric Functions?
Secant, cosecant and cotangent are the three reciprocal trigonometric functions, defined as sec theta = 1/cos theta, cosec theta = 1/sin theta and cot theta = 1/tan theta = cos theta/sin theta. Each is undefined wherever its denominator is zero, and each carries the same sign as the function it is the reciprocal of. They are reciprocals, not inverse functions: sec theta returns a ratio, whereas the inverse function cos to the power minus one returns an angle.
This definition is part of the Trigonometry chapter in Cambridge IGCSE Additional Mathematics.