Answer:
The value of x is 56.5 km.
Explanation:
In a right angled triangle the cosine ratio is defined as
![\cos\theta=(base)/(hypotenuse)=(adjacent)/(hypotenuse)](https://img.qammunity.org/2019/formulas/mathematics/high-school/9er1go3uypqyudhx6p7sytbqyixn19b0mp.png)
From the given figure it is clear that the adjacent sides of angle 28 degree is x and the measure of hypotenuse is 64 km.
![\cos(28^(\circ))=(x)/(64)}](https://img.qammunity.org/2019/formulas/mathematics/high-school/6f73io8h1xinvzjqha4i8b5l7wcgx61ad0.png)
![64* \cos(28^(\circ))=x](https://img.qammunity.org/2019/formulas/mathematics/high-school/1u7ex0tquzo3bl1uj5w2fy1sjn6fqexcdg.png)
![x=56.508645943](https://img.qammunity.org/2019/formulas/mathematics/high-school/vv12vx7urkpli7fl98ie4mkgnlkvbxqr19.png)
![x\approx 56.5](https://img.qammunity.org/2019/formulas/mathematics/high-school/92b5ml7kkjnja6q9xwjo6ccst4vn1upqkg.png)
Therefore the value of x is 56.5 km.