baloon.png
d2=d1+1.9
tan( 18.5 ) = h/d1
tan( 12.5 ) = h/d2
tan( 18.5 )*d1 = h
tan( 12.5 )*d2 = h
tan( 18.5 )*d1=tan( 12.5 )*d2
tan( 18.5 )*d1=tan( 12.5 )*(d1+1.9)
tan( 18.5 )*d1=tan( 12.5 )*d1+tan( 12.5 )*1.9
tan( 18.5 )*d1-tan( 12.5 )*d1=tan( 12.5 )*1.9
d1*(tan( 18.5 )-tan( 12.5 ))=tan( 12.5 )*1.9
d1=(tan( 12.5 )*1.9)/(tan( 18.5 )-tan( 12.5 ))
[input](tan( 12.5 )*1.9)/(tan( 18.5 )-tan( 12.5 ))[/input]
d1= 3.73088935653542mi
h = tan( 18.5 )*d1
[input]tan( 18.5 )*3.73088935653542[/input]
h=1.24833811627684120894 (Balloon height)
test:
d2 = d1+1.9 = 5.63088935653542
h = tan( 12.5 )*d2= 1.24833811627684143082 (check)
+3144 
