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If two planes are perpendicular to 'each other, a straight line drawn in one of them, perpendicular to their intersection, will be perpendicular to the other.
Elements of Geometry and Trigonometry: From the Works of A.M. Legendre - Page 172
by Adrien Marie Legendre - 1874 - 455 pages

## Elements of Geometry

Webster Wells - 1894 - 172 pages
...diedral PRQM. (§ 431.) Therefore, PQ is perpendicular to MN. (§ 435.) PROPOSITION XVIII. THEOREM. 440. If two planes are perpendicular to each other, a straight line drawn in one of them jjei'pendictdar to their intersection is perpendicular to the other. Let the plane PQ be perpendicular...

## The Elements of Geometry

Webster Wells - Geometry - 1894 - 398 pages
...diedral PRQM. (§ 431.) Therefore, PQ is perpendicular to MN. (§ 435.) PROPOSITION XVIII. THEOREM. 440. If two planes are perpendicular to each other, a straight line drawn in one of tltem perpendicular to their intersection is perpendicular to the other. Let the plane PQ be perpendicular...

## Syllabus of Geometry

George Albert Wentworth - Mathematics - 1896 - 68 pages
...their plane angles are equal. 513. Two dihedral angles have the same ratio as their plane angles. 515. If two planes are perpendicular to each other, a straight...in one of them perpendicular to their intersection is perpendicular to the other. 516. Cor. 1. If two planes are perpendicular to each other, a perpendicular...

## Elements of Geometry

Andrew Wheeler Phillips, Irving Fisher - Geometry - 1896 - 554 pages
...Since AB is perpendicular to CD and also to QS, it is perpendicular to MN. § 531 Q ED 576. COR. I. If two planes are perpendicular to each other, a straight line drawn perpendicular to one at any point of their intersection lies in the other. Hint. — In the foregoing...

## Elements of Geometry

George Washington Hull - Geometry - 1897 - 408 pages
...other parallel planes, the four lines of intersection arc parallel. PROPOSITION XXI. THEOREM. 412. If two planes are perpendicular to each other, a straight...one of them, perpendicular to their intersection, is perpendicular to tile other. Given—The plane PQ perpendicular to MN, and AB perpendicular to their...

## Elements of Geometry

Andrew Wheeler Phillips, Irving Fisher - Geometry - 1896 - 574 pages
...Since AB is perpendicular to CD and also to QS, it is perpendicular to MN. § 531 QED <5>76>. COR. I. If two planes are perpendicular to each other, a straight line drawn perpendicular to one at any point of their intersection lies in the other. Hint. — In the foregoing...

## Plane and Solid Geometry

James Howard Gore - Geometry - 1898 - 232 pages
...plane. 364. If the diedral angle is a right angle, the plane angle is also a right angle: therefore if two planes are perpendicular to each other, a straight...in one of them perpendicular to their intersection is perpendicular to the other. 365. The following principles are also true: 1. If a straight line is...

## Elements of Geometry: Geometry of space

Andrew Wheeler Phillips, Irving Fisher - Geometry - 1898 - 324 pages
...diedral angles are equal. § 572 That is, PQ is perpendicular to MN. § 570 QED PROPOSITION XVIII. THEOREM >. If two planes are perpendicular to each other, a straight line drawn in one, perpendicular to their intersection, is perpendicular to the other. GIVEN — the plane PQ perpendicular...