An astronomical object has an actual diameter of 128 km
and an apparent size of 24'16" as viewed from earth.
How far is this object from earth?
So, I converted into DD format and got
Your diagram is correct.
Bisect the vertex angle of that isosceles triangle.
You will have a right triangle.
One side runs from earth (E) to the center of the object (C).
. . Let
From the center directly to the right, CA is the radius of the object: 64 km.
. . And EA is the hypotenuse.
We have: .