12. 3ctg(π/4) · sin(π/6) − 2 cos(π/3) · tg(π/4)

Используем значения \(\ctg\frac{\pi}{4}=1\), \(\sin\frac{\pi}{6}=\frac12\), \(\cos\frac{\pi}{3}=\frac12\), \( g\frac{\pi}{4}=1\).

\(3\cdot1\cdot\frac12-2\cdot\frac12\cdot1=\frac32-1=\frac12.\)

Ответ: \(\frac12\).