Descriptive geometry . Fig. 158. Fig. 15it. But let the line A, Fig. 159, be perpendicular to the planeQ, and let us pass through A the plane T perpendicular to //. 94 DESCRIPTIVE GEOMETRY [XI, § 113 Since HT coincides with Ah, and Ah is perpendicular to HQ,it follows that HT is perpendicular to HQ. Hence we havethe proposition : If two planes are mutually perpendicular, and one of them isperpendicular to a coordinate plane, the traces of the two givenplanes on that coordinate plane are perpendicular. 114. Lines of Maximum Inclination to H and V. Let Q beany plane oblique to H. Those of its li

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Descriptive geometry . Fig. 158. Fig. 15it. But let the line A, Fig. 159, be perpendicular to the planeQ, and let us pass through A the plane T perpendicular to //. 94 DESCRIPTIVE GEOMETRY [XI, § 113 Since HT coincides with Ah, and Ah is perpendicular to HQ,it follows that HT is perpendicular to HQ. Hence we havethe proposition : If two planes are mutually perpendicular, and one of them isperpendicular to a coordinate plane, the traces of the two givenplanes on that coordinate plane are perpendicular. 114. Lines of Maximum Inclination to H and V. Let Q beany plane oblique to H. Those of its lines which are perpen-dicular to HQ have the peculiarity that they make with H agreater (acute) angle than any other lines in the plane. For this reason they are called the lines X. of maximum inclination to H of the \ plane Q. Let M, Fig. 160, be one V\ob °f these lines. Since M is perpen- V/\ dicular to HQ, it follows that Mh \ \^ must also be perpendicular to HQ. N. ^ / A plane is determined when one >^ J / of i

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectgeometrydescriptive