[681.] Definitions. I.
[682.] II.
[683.] III.
[684.] IV.
[685.] Corollaire.
[686.] PROPOSITION II. Theoreme.
[687.] Démonstration.
[688.] Corollaire.
[689.] PROPOSITION III. Théoreme.
[690.] Demonstration.
[691.] Corollaire I.
[692.] Corollaire II.
[693.] Corollaire III.
[694.] Corollaire IV.
[695.] PROPOSITION IV. Theoreme.
[696.] Demonstration.
[697.] Corollaire.
[698.] PROPOSITION V. Theoreme.
[699.] Demonstration.
[700.] Corollaire.
[701.] PROPOSITION VI. Theoreme.
[702.] Démonstration.
[703.] PROPOSITION VII. Theoreme.
[704.] PROPOSITION VIII. Théoreme.
[705.] Demonstration.
[706.] Remarque.
[707.] PROPOSITION IX. Probleme.
[708.] Solution.
[709.] PROPOSITION X. Probleme.
[710.] Solution.