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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 them, that is, to the plane in which they are.
Euclid's Elements: Or, Second Lessons in Geometry,in the Order of Simson's ... - Page 133
by Dennis M'Curdy - 1846 - 138 pages

## 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 two straight lines in the point of their intersection, it is also at right angles to the plane passing through them :...

## Annual Statement, Volumes 11-20

1876 - 646 pages
...figures having the same area what one has the least perimeter? 5. If a straight line is perpendicular to each of two straight lines at their point of intersection, it is perpendicular to the plane of those lines. 6. A triangular pyramid is one-third of a triangular...

## Elements of Geometry, Conic Sections, and Plane Trigonometry

Elias Loomis - Geometry - 1877 - 458 pages
...common section. Hence, if two planes, etc. PROPOSITION IV. THEOREM. If a straight line be perpendicular to each of two straight lines at their point of intersection, it will be perpendicular to the plane in which these lines are. Let the straight line AB be perpendicular to...

## Elements of Descriptive Geometry

J. B. Millar - Geometry, Descriptive - 1878 - 264 pages
...another, their common section is a straight line 2 Theorem III. If a straight line be perpendicular to each of two straight lines at their point of intersection, it shall also be perpendicular to their plane 3 Theorem IV. Every plane which contains the normal to another...

## The Elements of Plane and Solid Geometry: With Chapters on Mensuration and ...

Isaac Sharpless - Geometry - 1879 - 282 pages
...the plane BC; it is therefore their common section. Proposition 4. Theorem.—If a straight line be at right angles to each of two straight lines at their point of intersection, it is at right angles to the plane in which these straight lines are. Let AB be at right angles to each...

## 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...

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

Oxford univ, local exams - 1880
...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...straight lines at their point of intersection, it shall also be at right angles to the plane which passes through them, that is, to the plane in which...

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

Isaac Todhunter - Euclid's Elements - 1880 - 400 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...