Answer:
Using Pythagoras theorem:
.
We know that:
The radius of a circle meets a tangent at 90 degree
Labelled the triangle as A, B and C as shown below;
In rt angle triangle ABC:
Opposite side = AB = x units
Adjacent side = BC = 3959 mi
Hypotenuse side=AC = 3959 +2.9 = 3961.9 mi
Using Pythagoras theorem;

then;


⇒

⇒

Simplify:
151.560549 = x
or
x = 151.6 mi
Therefore, the distance to the horizon From the climber’s viewpoint is, 151.6 mi