Question

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Explanation:

Step1: Use cosine function

In a right - triangle, $\cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}}$. Here, $\theta = 60^{\circ}$ and the adjacent side to the $60^{\circ}$ angle is 5, and the hypotenuse is $x$. So, $\cos60^{\circ}=\frac{5}{x}$.

Step2: Recall cosine value

We know that $\cos60^{\circ}=\frac{1}{2}$. So, $\frac{1}{2}=\frac{5}{x}$.

Step3: Solve for $x$

Cross - multiply to get $x = 10$.

Answer:

$x = 10$