T H E E L E M E N T S |
Book II Proposition 10 | |
Then, since a straight line EF falls on the parallel straight lines EC, FD, the angles CEF, EFD are equal to two right angles; [I.29] therefore the angles FEB, EFD are less than two right angles. But straight lines produced from angles less than two right angles meet; [I. Post.5] therefore EB, FD, if produced in the direction B, D, will meet. Let them be produced and meet at G, and let AG be joined. |
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