To determine how high the kite is flying vertically above the point at which the string is being held, we can use trigonometry.
Given that the string forms a 45° angle with the ground and the length of the string (hypotenuse) is 100 ft, we can use the sine function to find the vertical height (opposite side):
\[ \text{height} = \text{hypotenuse} \times \sin(\theta) \]
Substituting the known values:
\[ \text{height} = 100 , \text{ft} \times \sin(45°) \]
Since \(\sin(45°) = \frac{\sqrt{2}}{2}\):
\[ \text{height} = 100 , \text{ft} \times \frac{\sqrt{2}}{2} = 50\sqrt{2} , \text{ft} \]
Thus, the height of the kite vertically above the point where the string is held is:
\[ 50\sqrt{2} , \text{ft} \]
So the correct response is: 50 Start Root 2 End Root ft.