Find the exact value of each of the remaining trigonometric functions of $\theta$. Rationalize denominators when applicable.
$\sin \theta=-\frac{\sqrt{3}}{5}$ given that $\theta$ is in quadrant IV
Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
A. $\cos \theta=$
(Simplify your answer, including any radicals. Use integers or fractions for any numbers in the expression.)
B. The function is undefined

Step 1 ：We are given that \(\sin \theta = -\frac{\sqrt{3}}{5}\) and \(\theta\) is in quadrant IV.

Step 2 ：We can use the Pythagorean identity \(\sin^2 \theta + \cos^2 \theta = 1\) to find the value of \(\cos \theta\).

Step 3 ：In quadrant IV, cosine is positive. Therefore, we can solve for \(\cos \theta\) by taking the positive square root of \(1 - \sin^2 \theta\).

Step 4 ：Substituting the given value of \(\sin \theta\) into the equation, we get \(\cos \theta = \sqrt{1 - \left(-\frac{\sqrt{3}}{5}\right)^2}\).

Step 5 ：Solving the equation, we find that \(\cos \theta = 0.938083151964686\).

Step 6 ：Final Answer: \(\boxed{0.938083151964686}\)