Question 144669
cot90=0 it can directly be obtained from its trigonometric relation already proved which says that cotx={{{sin(x)/cos(x)}}}.so we can get the value of cot90 from this formula.Now
cot90={{{cos90/sin90}}}
cot90={{{0/1}}}    because cos90=0 and sin90=1 
hence we have shown that cot90=0