# I have confusion between undefined and infinite. For example,tan 90 degrees is undefined or infinite?Please clarify my doubt.

Ajay
209 Points
6 years ago
Tha 90 is undefined because tan90 have different values when we approach it from different side of 90 as shown. Since there right hand and left hand limits of tanx at x= 90 are not same, tan90 is not deifined.

$\lim _{ h->0 }{ \quad tan(90+h)\quad } =\quad \lim _{ h->0 }{ \quad -cot(h) } \quad =\quad -\infty \\ \lim _{ h->0 }{ \quad tan(90-h)\quad } =\quad \lim _{ h->0 }{ \quad cot(h) } \quad =\quad +\infty$