The terminal side of an angle, $\theta$ passes through the point $(-4,-6)$. Use the diagram to answer the following question.

Find the value of $\cos \theta$. Rationalise the denominator if necessary.

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: The terminal side of an angle, $\theta$ passes through the point $(-4,-6)$. Use the diagram to answer the following question.

Find the value of $\cos \theta$. Rationalise the denominator if necessary.

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: The terminal side of an angle, $\theta$ passes through the point $(-4,-6)$. Use the diagram to answer the following question.

Find the value of $\cos \theta$. Rationalise the denominator if necessary.
