Explain why some trigonometric identities have restrictions or non-permissible

Question

values. What are the restrictions for each of the reciprocal trigonometric ratios?

help

Answer 1

If a trig function has a value of zero for a given angles, then clearly its
reciprocal will be undefined.
e.g. cos 90° = 0
then sec 90 = 1/0 which is undefined
e.g. tan 180° = 0, so cot 180° will be undefined.

So, whenever the graph of a trig function crosses the x-axis, that is,
when its value is zero, then its reciprocal function will be undefined for
that value of x

Answer 2

thank you so much!