Question

Which trigonometric functions are undefined when x = 0?

Answer 1

First, the the secant, cosecant, and cotangent functions are the reciprocals of the cosine, sine, and tangent functions, respectively. Second, there is novalue for which the cosine and sine functions are undefined. This is because r is the distant from the origin to the point (x,y) ≠ (0,0) on the terminal ray.