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If a straight line is perpendicular to each of two straight lines at their point of intersection, it is perpendicular to the plane of those lines.
Elements of Geometry: With Practical Applications to Mensuration - Page 170
by Benjamin Greenleaf - 1868 - 320 pages

## The Teaching of Mathematics in the United Kingdom

Great Britain. Board of Education - Mathematics - 1912 - 632 pages
...of two similar triangles is equal to 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...

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

Great Britain. Board of Education - Education - 1912 - 1048 pages
...of two similar triangles is equal 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, and...

## Solid Geometry

Clara Avis Hart, Daniel D. Feldman - Geometry, Solid - 1912 - 220 pages
...SOLID GEOMETRY PROPOSITION IV. THEOREM If a straight line is perpendicular to each of two intersecting straight lines at their point of intersection, it is perpendicular to the plane of those lines. Given str. line FB±AB and to BC at B, and plane MN containing AB and BC. To prove...

## Elements of Solid Geometry

William Herschel Bruce, Claude Carr Cody - Geometry, Solid - 1912 - 134 pages
...greater distance from the foot of the perpendicular. PROPOSITION III. THEOKEM. 535. A straight line perpendicular to each of two - straight lines at their point of intersection is perpendicular to the plane of those lines. M f Given AB _L BC and BD at B. To prove AB _L MN, the...

## Plane and Solid Geometry

George Albert Wentworth, David Eugene Smith - Geometry - 1913 - 496 pages
...perpendicular to the line. PROPOSITION II. THEOREM 431. If a line is perpendicular to each of two other lines at their point of intersection, it is perpendicular to the plane of the two lines. Given the line AO perpendicular to the lines OP and OR at 0. To prove that AO is...

## Plane and Solid Geometry

George Albert Wentworth, David Eugene Smith - Geometry - 1913 - 500 pages
...perpendicular to the plane. PROPOSITION II. THEOREM 431. If a line is perpendicular to each of two other lines at their point of intersection, it is perpendicular to the plane of the two lines. Given the line AO perpendicular to the lines OP and OR at 0. To prove that AO is...

## Schultze and Sevenoak's Plane and Solid Geometry

Arthur Schultze, Frank Louis Sevenoak - Geometry - 1913 - 486 pages
...plane. SOL7D GEOMETRY PROPOSITION VIII. THEOREM 499. If a straight line is perpendicular to each of two lines at their point of intersection, it is perpendicular to the plane of those lines. Given BC and BD _L AB, and plane MN containing BC and BD. To prove AB _L plane MN....

## Plane and Solid Geometry

George Albert Wentworth, David Eugene Smith - Geometry - 1913 - 491 pages
...perpend-icular to the plane. PROPOSITION II. THEOREM 431. If a line is perpendicular to each of two other lines at their point of intersection, it is perpendicular to the plane of-the two lines. Given the line AO perpendicular to the lines OP and OR at 0. To prove that AO is...