Because angle lies in second quadrant (negative x axis and positive y axis) we can straight away tell that cos(teta) is negative and tan(teta) is also negative
cos(teta) = [tex] \sqrt{1 - sin(teta)^{2} } [/tex] = -4/5
Sin(teta) cannot be larger than 1 so I assume you wanted to say 3/5 because that fits offered answers.
tan(teta) = sin(teta)/cos(teta) = -3/4
