using trigonometry
The force in the wire corresponds to the hypotenuse in a right-angled triangle. The angle is 40°. The vertical force of 5 N is adjacent to the angle of 40°. So, the cosine is used.
$${ 5 N = F_{wire} \cdot \cos{40°} }$$
So,
$${ F_{wire} = \frac{5 N}{\cos{40°}} \approx 6.53 N }$$
