3. Вычислите: 6 cos²(π/4) + tg²(−π/3) − ctg²(−π/2).

\(\cos^2\frac{\pi}{4}=\frac12\), \( g^2\left(-\frac{\pi}{3}\right)=3\), а \(\ctg\left(-\frac{\pi}{2}\right)=0\).

\(6\cdot\frac12+3-0=6\).

Ответ: 3) 6.