1) 2sinX = - 1

3) tg ( = - 1

1) 2sinX = - 1
sinx = - 1/2
x = (-1)^n*arcsin(-1/2) + πn, n∈z
x = (-1)^(n+1)*arcsin(1/2) + πn, n∈z
x = (-1)^(n+1)*(π/6)+ πn, n∈z

3) tg (π/2 - x)  = - 1
ctgx = - 1
x = - π/4 = πk, k∈Z