Question

is that true if, y=-(sinx) then -arcsiny=x. ?

Answer 1

Yes, because sin is an odd function. You can test the statement by plugging in values. Try pi/2:
y = -(sin(pi/2)) = -1
x = -arcsin(-1) = pi/2

Answer 2

y=-(sinx) = sin(-x)
then
-x= arcsiny
x=-arcsiny