sin θ = 3 / 7 = .429
sin^2 θ + cos^2 θ = 1 trig identity
9/49 + cos^2 θ = 1
cos^2 θ = 40 / 49 = .816 cos θ = .903
Check .429^2 + .903^2 = 1
cos .903 = 25.4 deg
In the second quadrant sin = +, cos = -, tan = -
So 25.4 deg in the second quadrant = 180 - 25.4 = 154.6 deg
Check:
sin 154.6 = .428
cos 154.6 = -.903
tan 154.6 = -.475
