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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

## Calendar

...the mid-point of BC. AE cuts the diagonal BD in F. Prove that BF is £ BD. 11. If a straight line be at right angles to each of two straight lines at their point of intersection it shall be at right angles to the plane containing them. From a point P are drawn lines PA, PB perpendicular...

## A Text-book of Euclid's Elements for the Use of Schools, Book 1

Euclid - Euclid's Elements - 1904 - 456 pages
...perp. to this plane. QED PROPOSITION 4. THEOREM. [Euclid-s Proof.] If a straight line is perpendicular to each of two straight lines at their point of intersection, it shall also be perpendicular to the plane in which they lie Let the st. line EF be perp. to each of...

## Examinations Papers

1907
...the segments of the base and that contained by the sides of the triangle. 7. If a straight line be at right angles to each of two straight lines at their point of intersection, it is perpendicular to the plane in which they lie. AS and BC are two straight lines at right angles,...

## Special Reports on Educational Subjects, Volumes 26-27

Great Britain. Board of Education - Education - 1912 - 1032 pages
...tothe ratio of the squares on corresponding sides. 9. Show that, if a straight line is perpendicular to each of two straight lines at their point of intersection, it is also perpendicular to the plane in which they lie. OXYZ is a tetrahedron such that OX = OY = OZ,...

## The Teaching of Mathematics in the United Kingdom

...the ratio of the squares on corresponding sides. 9. Show that, if a straight line is perpendicular to each of two straight lines at their point of intersection, it is also perpendicular to the plane in which they lie. OXYZis a tetrahedron such that OX = 0Y= OZ, and...

## Journal of Education

Education - 1914 - 912 pages
...and the diameter of the circle described about the triangle. 6. If a straight line is perpendicular to each of two straight lines at their point of intersection, it shall also be perpendicular to the plane in which they lie. 7. If a pyramid is cut by planes drawn...

## Oxford, Cambridge and Dublin Messenger of Mathematics, Volume 5

Mathematics - 1871 - 280 pages
...are the middle points of the sides and A,B,C the intersections of opposite sides. EUCLID XI., &c. I. 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 angUs to the plane which passes through...