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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.
Solutions of the Cambridge Problems, from 1800 to 1820 - Page 653
by John Martin Frederick Wright - 1836

The New Cambridge Guide ; Or, A Description of the University, Town and ...

Cambridge (England) - 1804 - 476 pages
...both by vulgar fractions and by decimals. 2. ^Prove that if a straight line stand at right arfgles to each of two straight lines in the point of their intersection, it will be at right angles to the plane that passes through them. 3. Define a rhombus; and prove that...

The Elements of Euclid: The Errors, by which Theon, Or Others, Have Long Ago ...

Robert Simson - Trigonometry - 1806 - 518 pages
...planes AB, BC cannot but be a straight line. Wherefore, if two planes, &c. QED PROP. IV. THEOR. SeeN. IF a straight line stand at right angles to each of...the point of their intersection, it shall also be at ri^ht angles to the plane which passes through them, that is, to the plane in which they are. Let the...

Elements of Geometry: Containing the First Six Books of Euclid, with a ...

John Playfair - Euclid's Elements - 1806 - 320 pages
...is the common section of these planes. Therefore, if two planes, &c. QED A PROP. IV. THEOR. a 2. 6. IF a straight line stand at right angles to each of...straight lines in the point of their intersection, it will also be at right angles to the plane in which these lines are. Let the straight line AB stand...

The Elements of Euclid: Viz. the First Six Books, Together with the Eleventh ...

Euclid - Geometry - 1810 - 518 pages
...perpendicular to DE: therefore AF is perpendicular '-*">'•~>•' to each of the straight lines GH, DE. But if a straight line stand at right angles to each of...intersection, it shall also be at right angles to the plane passing through them. But the plane passing through ED, GH is the plane BH; therefore AF is perpendicular...

Pantologia. A new (cabinet) cyclopędia, by J.M. Good, O. Gregory ..., Volume 5

John Mason Good - 1813 - 722 pages
...III. Theor. If two planes cut one another, their common section is a straight line. Piop. IV. Theor. If a straight line stand at right angles to each of...right angles to the plane which passes through them, that is, to> the plane in which they are'. Prop. V. Theor. (f three straight lines meet аЦ in one...

The Elements of Euclid; viz. the first six books, together with the eleventh ...

Euclides - 1814 - 558 pages
...DE: Therefore AF is perpendicular to each of the straight Hues GH, DC. But if a straight line stands at right angles to each of two straight lines in the point of their intersection, it shall »lso be at right angles to the plane passing through them. But the plane passing through ED, GH, is...

The Elements of Euclid: Viz. the First Six Books, Together with the Eleventh ...

Euclides - 1816 - 528 pages
...DE : ThereforeAFis perpendicular to each of the straight lines GH, DE. But if a straight line stands at right angles to each of two straight lines in the...intersection, it shall also be at right angles to the plane passing through them. But the plane passing through ED, GH, is the plane BH i therefore AF is perpendicular...

Pantologia. A new (cabinet) cyclopędia, by J.M. Good, O. Gregory ..., Volume 5

John Mason Good - 1819 - 740 pages
...one another, their common section is a straight line. Prop. IV. Theor. If a straight line stand it right angles to each of two straight lines in the...right angles to the plane which passes through them, that is, 10 the plane in which they are. Piop. V. Theor. If three straight lines meet i!i in one point,...