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If a straight line stand at right angles to each of two straight lines in the point of their intersection, it will also be at right angles to the plane in which these lines are.
An elementary course of mathematics - Page 5
by Samuel Hunter Christie - 1847

## Elements of geometry, containing books i. to vi.and portions of books xi ...

Euclides, James Hamblin Smith - Geometry - 1872 - 376 pages
...MN. QED Note. — The Propositions which follow are numbered as in Euclid. PROPOSITION IV. THEOREM. If a straight line stand at right angles to each of two straight lines, at the point of their intersection, it must also be at right angles to the plane that passes through...

## The Elements of Euclid, containing the first six books, with a selection of ...

Euclides - 1874 - 342 pages
...AB and BC, must be in a straight line. Wherefore, if two planes, &c. QED PROPOSITION 4. — Theorem. If a straight line stand at right angles to each of two straight lines at. the point of their intersection, it is at right angles to the plane in which they are. Let the...

## Euclid's Elements of Geometry: Chiefly from the Text of Dr. Simson, with ...

Robert Potts - Geometry - 1876 - 446 pages
...and AFis perpendicular to DE; therefore AFis perpendicular to each of the straight lines GH, DE. But if a straight line stand at right angles to each of...straight lines in the point of their intersection, it is also at right angles to the plane passing through them : (xi. 4.) but the plane passing through...

## Solutions of the Cambridge Senate-house Problems and Riders for the Year 1875

Sir George Greenhill - Mathematics - 1876 - 318 pages
...perpendiculars from B and D on FA are equal, and therefore FA bisects BD, and its parallel CE. •vi. If a straight line stand at right angles to each of two straight lines at the point of their intersection, it shall also be at right angles to the plane which passes through...

## Elements of Geometry: Containing Books 1. to Vi. and Portions of Books Xi ...

James Hamblin Smith - Euclid's Elements - 1879 - 378 pages
...0, ED Note. — The Propositions which follow are numbered as in iluolid. PROPOSITION IV. THEOREM. If a straight line stand at right angles to each of two i lines, at the point of their intersection, it must also be at right angles to the plane that passes...

## Military examinations. Mathematical examination papers, set for entrance to ...

Woolwich roy. military acad, Walter Ferrier Austin - 1880 - 190 pages
...sides, find the area of the polygon, and hence prove that Trr2 is the area of a circle of radius r. 1. If a straight line stand at right angles to each of two straight lines at the point of their intersection, it shall be at right angles to the plane which passes through them....

## Examination papers, and division lists, &c. [afterw.] General certificate of ...

Oxford univ, local exams - 1880 - 396 pages
...figure inscribed in a circle is equal to the sum of the rectangles contained by its opposite sides. 12. If a straight line stand at right angles to each of two straight lines at their point of intersection, it shall also be at right angles to the plane which passes through...

## The Elements of Euclid for the Use of Schools and Colleges: With Notes, an ...

Isaac Todhunter - Euclid's Elements - 1880 - 426 pages
...planes AB and BC cannot but be a straight line. Wherefore, if two planes &c. QED PROPOSITION 4. THEOREM. If a straight line stand at right angles to each of two straight lines at the point of their intersection, it shall also be at right angles to the plane which passes through...