4.7. sin α = −0,6, π < α < 3π/2.

\(\sin\alpha=-0.6=-\frac{3}{5}\). В III четверти cos α < 0:

\(\cos\alpha=-\frac{4}{5}\), \( g\alpha=\frac{3}{4}\), \(\ctg\alpha=\frac{4}{3}\).

Ответ: cos α = −4/5; tg α = 3/4; ctg α = 4/3.