Question number 30 please solve step by step.........................

lim (x->pi/2) [ (x - pi/2)/Cosx ]  
Put x - pi/2 = y 
as x tending ti pi/2  y tending to zero 
lim (y->0) (y /Cos(pi/2 +y) 
lim (y-> 0) (y/-siny) 
= take y in denominator of siny and apply limit 
so , Lim (y->0) Siny/ y = 1 
Ans = -1 
Hope this helps 
Good Luck