Attatched is a diagram that I've made of the triangle formed by the kite, the ground and the pole. So, we are trying to find angle CAB. Notice that we know the side adjacent to the angle and the hypotenuse, so we can use cosine:
[tex] \cos{CAB}=\frac{50}{160} \implies\\
CAB=\arccos{\frac{50}{160}} =71.7900431^{\circ} \approx 71.79^{\circ} [/tex]
The string forms an angle of 71.79 degrees with the ground.
