Question

cossec 90º - cossec $\pi /2$

Answer 1

$90^o=\frac{\pi}{2}\\ \\ Logo:\\ \\ cossec90^o-cossec \frac{\pi}{2}=0$

Answer 2

pi/2 = 180º/2 = 90º
cossec = 1/seno

seno90º=1

1/1 - (1/1) = 1 - (1) = 0