...equal to the product of its three sides divided by twice the diameter of the circumscribed circle. 104. The rectangle contained by the diagonals of a quadrilateral...equal to the sum of the two rectangles contained by the opposite sides. 105. If a perpendicular is drawn from the vertex of a triangle ABC, to the base...

...Enclid's definition of proportion, and from it deduce the Algebraical definition of proportion. 2. Prove that the rectangle contained by the diagonals of a quadrilateral inscribed in a circle is equal to both the rectangles contained by its opposite sides. 3. Prove, by geometry, that the geometrical mean...

...base and the diameter of the circumscribing circle. VI. D. — Ptolemy's Theorem. The rectangle of the diagonals of a quadrilateral inscribed in a circle is equal to both the rectangles under the opposite sides. BOOK XL XI. 4. — A right line perpendicular to two...

...££.a*. §278 EA AC :.BA X AC = EA X AD. QED PROPOSITION XX. THEOREM. 301. The product of the two diagonals of a quadrilateral inscribed in a circle is equal to the sum of the products of its opposite sides. J3 Let ABC D be any quadrilateral inscribed in a circle, AC and BD...

...triangle, the base, vertical angle, and the rectangle contained by the sides: construct it. PROP. 95. The rectangle contained by the diagonals of a quadrilateral inscribed in a circle is equal to the sum of the rectangles contained by the opposite sides. Let ABCD be a quadrilateral inscribed in a circle : then...

...subject, he gives there the theorem, afterwards inserted in Euclid (book vi. prop. D), relating to the rectangle contained by the diagonals of a quadrilateral inscribed in a circle. The Arabians made the improvement of using, in place of the chord of an are, the sine, or half chord...

...8. In the same figure prove AB . AD + CB . CD : BA . BC + DA . DC = AC:BD. PROPOSITION D.* THEOREM. The rectangle contained by the diagonals of a quadrilateral...the two rectangles contained by its opposite sides. A Let ABCD be a quadrilateral inscribed in a circle, and AC, BD its two diagonals : it is required...

...Some of these Ptolemy first sets out. He next proves the proposition, now appended to Euclid vi. (D), that " the rectangle contained by the diagonals of a quadrilateral inscribed in a circle is equal to both the rectangles contained by its opposite sides1", and then proceeds to shew how from the chords...

...the subject he gives there the theorem afterwards inserted in Euclid (Book VI. Prop. D) relating to the rectangle contained by the diagonals of a quadrilateral inscribed in a circle. The Arabians made the improvement of using in place of the chord of an arc the sine, or half chord...

...angles of a triangle are equal, the triangle is isosceles. (4). The sum of one pair of opposite angles of a quadrilateral inscribed in a circle is equal to the sum of the remaining pair. For, join the pole of the circle to the angles of the quadrilateral forming four isosceles...