Question

Arcsin0+arccos0+arctg0

Answer 1

arcsin0+arccos0+arctg0=0+π/2+0=π/2

Answer 2

$arcsin0+arccos0+arctg0=0+ frac{ pi }{2} +0= frac{ pi }{2}$

$arcsin0= alpha$
$sin alpha =0$
$alpha =0$

$arccos0= beta$
$cos beta =0$
$beta = frac{ pi }{2}$

$arctg0=k$
$tgk=0$ 
$k=0$