17. sin(π/4) = cos(π/4) = √2/2; tg(π/4) = 1; ctg(π/4) = 1

Для угла \(\frac{\pi}{4}\) синус и косинус равны, поэтому \( g\frac{\pi}{4}=\frac{\sin\frac{\pi}{4}}{\cos\frac{\pi}{4}}=1\), а \(\ctg\frac{\pi}{4}=\frac{\cos\frac{\pi}{4}}{\sin\frac{\pi}{4}}=1\).

Ответ: \(\sin\frac{\pi}{4}=\cos\frac{\pi}{4}=\frac{\sqrt2}{2}\), \( g\frac{\pi}{4}=1\), \(\ctg\frac{\pi}{4}=1\).