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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

## 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 two straight lines in the point of their intersection, it shall also be at ri^ht angles to the plane which passes through...

## 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 two straight lines in the point of their intersection, it will also be at right angles to the plane in which these lines...

## 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 two straight lines in the point of their intersection, it shall also be at right angles to the plane which passes through...

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

Euclides - 1814 - 558 pages
...AB, N BC, cannot but be a straight line. Wherefore, if two planes, &c. QED PROP. IV. THEOR. SeeN. IP a straight line stand at right angles to each of two straight lines in the point of their intersection, it shall also be at right angles to the plane which passes through-them,...

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

Euclides - 1816 - 528 pages
...planes AB, BC, cannot but be a straight line. Wherefore, if two planes, &c. QED PROP. IV. THEOR. SeeN. straight line stand at right angles to each of two straight lines in the point of their intersection, it shall also be at right angles to the plane which passes through...

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

Euclid, John Playfair - Circle-squaring - 1819 - 348 pages
...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 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...

## Cambridge Problems: Being a Collection of the Printed Questions Proposed to ...

Mathematics - 1821 - 425 pages
...yards cost £2%, find the value of 5-f yards lx>th by vulgar fractions and by decimals. 2. Prove that if a straight line stand at right angles 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....

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

Robert Simson - Trigonometry - 1827 - 513 pages
...AB, BC, cannot but be a straight line. Wherefore, if two planes, &c. Q. E, D. PROP. IV. THEOR. See N. If a straight line stand at right angles to each of two straight lines in the point of their intersection, it shall also be at right angles to the plane which passes through...