55. Agar cosα=7/8 ga teng bo‘lsa, sinα ni toping.

\(\sin\alpha=\sqrt{1-\cos^2\alpha}=\sqrt{1-\frac{49}{64}}=\sqrt{\frac{15}{64}}=\frac{\sqrt{15}}8\).

Javob: \(\frac{\sqrt{15}}8\) (B).