If \(\sin \theta = a/b\), then \(\cos \theta\) is equal to:
Answer: C
Using the identity \(\sin^2 \theta + \cos^2 \theta = 1\):
\((\frac{a}{b})^2 + \cos^2 \theta = 1\)
\(\cos^2 \theta = 1 - \frac{a^2}{b^2} = \frac{b^2-a^2}{b^2}\)
\(\cos \theta = \sqrt{\frac{b^2-a^2}{b^2}} = \frac{\sqrt{b^2-a^2}}{b}\).