Question 161159
AB, BE, and AE form a right triangle with the right angle at the point of tangency (B)


BE is the radius (r) of the Earth __ AE is the radius (r) plus the altitude of the satellite


using Pythagoras __ AB^2+BE^2=AE^2 __ 15977^2+r^2=(r+12500)^2 __ 15977^2+r^2=r^2+25000r+12500^2


subtracting r^2+12500^2 __ 15977^2-12500^2=25000r __ dividing by 25000 __ 3961=r (approx)