T
H
E

E
L
E
M
E
N
T
S
Book I   Proposition 36
For
    let BE, CH be joined.

Then, since
    BC is equal to FG (hypothesis) while EH is equal to FG,
    BC is also equal to EH. [C.N.1]

But they are also parallel. And EB, HC join them;
    but straight lines joining equal and parallel straight lines (at the extremities which are) in the same directions (respectively) are equal and parallel. [I.33]

Therefore
    EBCH is a parallelogram. [I.34]
Previous Page    Return to Propositions    Next Page