the sin ∅ is negative so ∅ belong to the III or IV quadrant but 180°< ∅ < 270° hence ∅ belong to the III quadrant sin ∅=-0.7660 sin² ∅+cos² ∅=1 cos² ∅=1-sin² ∅------> cos² ∅=1-(0.7660)²-----> 0.4132 cos ∅=√0.4132-----> cos ∅=0.6428 the value of cos ∅ is negative-------> III quadrant cos ∅=-0.6428
tan ∅=sin ∅/ cos ∅----> tan ∅=-0.7660/-0.6428----> tan ∅=1.1917
