mohon bantuannya dong nomor 1b beserta cara pengerjaannya

1/cos x + akar2 = 0
(akar2cosx + 1)/cos x = 0
akar2 cos x + 1 = 0
akar2 cos x = -1
cos x = -1/akar2
cos x = cos 135° , 225°
Jadi x = 135° , 225°