For this, we'll be using the trig. function tangent.
Tangent is the opposite over the adjacent (TOA)
x=15*tan(70) = x=18.329
The antenna is 18' to the nearest foot. (Rounding 18.3 to the nearest foot brings us to 18)
EDIT: My answer is incorrect, at least if it's in degrees (which it is).
The correct answer is 41'.
Definitely shows the importance of changing the mode!
tan (70 ° ) = height / base ength
tan (70°) = height / 15 multiply both sides by 15
15 * tan (70°) = height ≈ 41 ft
I think Rarinstraw just forgot to change the "mode" button on the calculator from rads to degrees.....a mistake easily made !!!