H
E
E
L
E
M
E
N
T
S
MF has the same ratio to each of the figures NH, SR;
therefore
NH is equal to SR. [V.9]
But
it [NH] is also similar and similarly situated to it [SR];
therefore
GH is equal to QR.
And, since,
as AB to CD, so is EF to QR, while QR is equal to GH,
therefore
as AB is to CD, so is EF to GH.
