Question 1092730
For {{{pi/2}}} or {{{90}}} degrees, 
{{{cos(pi/2)=0}}}
{{{sin(pi/2)=1}}}
So then 
{{{tan(pi/2)=sin(pi/2)/cos(pi/2)}}}
{{{tan(pi/2)=1/0}}}
So {{{tan(pi/2)}}} is undefined.