presupunem notatia clasuica, AB||CD,AB>CD
fie DD'⊥AB, CC'⊥AB, D',C'∈AB
notand BC'=x, avem AD'=30-15-x=15-x
exprimamDD' si CC" cu aj teo Pitagora
9²-(15-x)²=12²-x²
81-225+30x-x²=144-x²
30x=144-81+225
30x=144+144
10x=48+48
10x=96
x=9,6
atunci
CC' ²=12²-9,6²==51,84
verificare
AD'=15-9,6=5,4
DD' ²=9²-5,4²=51,84
deci x a fost bine aflat
atunci CC'=DD"=inaltimea=√51,84=7,2cm
