How do you determine the height of a mast?

You can determine the height of a mast by using the tangent. Measure the distance from the base, and the angle of elevation of the top of the mast as observed from that distance. The tangent is y over x, so substitute x for the distance from the base and y for the height of the mast. Solve from there.

For instance, if the angle is 60 degrees and the x distance is 25 feet, then...

tan (60) = y / 25
25 tan (60) = y
y = 43.3