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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

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

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 - 546 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 - Mathematics - 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 - 554 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...

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

Euclides - 1814 - 560 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 ğlso 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 - 588 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...

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

John Playfair - Circle-squaring - 1819 - 350 pages
...common to the planes AB and BC, or it is the common section of these planes. Therefore, &c. Q,. ED PROP. IV. THEOR. If a straight line stand at right...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...

## Elements of Geometry: Containing the First Six Books of Euclid: With a ...

John Playfair - 1819 - 354 pages
...common to the plnnes AB and BC, or v it is the common section of these planes. Therefore, &c. Q,. ED PROP. IV. THEOR. If a straight line stand at right angles to each of too straight lines in the point of their intersection, it will also be at right angles to the plane...