Answer:
630 .18 feet tall is the gateway arch .
Explanation:
As given
The angle of elevation from a park bench 778 feet from the base of the Gateway Arch in St. Louis, Missouri is 39 degrees.
Now by using the trignometric property

As diagram is given below .


CB = 778 feet


AB = 0.81 × 778
AB = 630 .18 feet
Therefore the 630 .18 feet tall is the gateway arch .