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For the same reason, CD is likewise at right angles to the plane HGK. Therefore AB, CD are each of them at right angles to the plane HGK.
An elementary course of mathematics - Page 13
by Samuel Hunter Christie - 1847

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

Euclid - 1835 - 540 pages
...therefore AB is at right angles" to the plane HGK. For ^ b8.ll. the same reason, CD is likewise ^i ~v~ -r\ at right angles to the plane •*^ HGK. Therefore...each of them at right angles to the plane HGK. But two straight lines, which are at right angles to the same plane, are parallel0 to one another. Therefore...

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

John Playfair - Euclid's Elements - 1835 - 336 pages
...parallel to AB ; therefore AB is at right . H T> angles (7. 2. Sup.) to the plane •" "c •" HGK. For the same reason, CD is likewise at right angles to the plane HGK. Therefore AB, CD JJ ... are each of them at right angles / to the plane HGK. But if two / straight lines are at right...

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

John Playfair - Euclid's Elements - 1836 - 488 pages
...therefore AB is at right II -13 a 4. 2. Sup. b 7. 2. Sup. E•F angles b to the plane HGK. For the same A reason, CD is likewise at right angles to the plane...Therefore AB, CD are each of them at right angles to the Cplane HGK. But if &two straight lines are at right angles to the same plane, they are parallel0 to...

## Solid and Spherical Geometry and Conic Sections: Being a Treatise on the ...

A. Bell - Conic sections - 1837 - 180 pages
...through them ; and EF is parallel to AB ; therefore AB is at right angles (I. 7) to the plane HGK. For the same reason, CD is likewise at right angles...right angles to the same plane, they are parallel (I. 6) to one another. Therefore AB is parallel to CD. PROPOSITION IX. THEOREM. If two straight lines...

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

John Playfair - Euclid's Elements - 1837 - 332 pages
...them : and EF is parallel to AB ; therefore AB is at right „ angles (7. 2. Sup.) to the plane A HGK. For the same reason, CD is likewise at right angles to the plane HGK. Therefore AB, CD jj \ -, are each of them at right angles ~* ' to the plane HGK. But if two straight lines are at right...

## The First Six and the Eleventh and Twelfth Books of Euclid's Elements: With ...

Euclid, James Thomson - Geometry - 1837 - 410 pages
...in the same plane. Therefore, if three straight lines, &c. PROP. VI. THEOR. IF two straight lines be at right angles to the same plane, they are parallel to one another. Let the straight lines AB, CD be at right angles to the same plane BDE ; AB is parallel to CD. Let...

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

Robert Simson - Geometry - 1838 - 434 pages
...through them: and EF is parallel to AB, therefore AB is at right angles (8. 11.) to the plane HGK. For the same reason, CD is likewise at right angles...each of them at right angles to the plane HGK. But _, if two straight lines be at right angles K D to the same plane, they shall be parallel (6. 11.)...

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

Euclides - Geometry - 1841 - 378 pages
...through them: and EF is parallel to AB; therefore •3 11. AB is at right angles* to the plane HGK: for the same reason, CD is likewise at right angles...lines are at right angles to the same plane, they are * 6.11. parallel • to one another: therefore AB is parallel to CD. Wherefore, two straight lines,...