Given that \(\theta\) is an acute angle and sin \(\theta\) = \(\frac{m}{n}\), find cos \(\theta\)

• A.\(\frac{\sqrt{n^2 - m^2}{m}\)
• B.\(\frac{\sqrt{(n + m)(n - m)}{n}\)
• C.\(\frac{m}{\sqrt{n^2 - m^2}\)
• D.\(\sqrt{\frac{n}{n^2 - m^2}}\)
• E.