Beman, Wooster Woodruff, 1850-1922, Smith, David Eugene, 1860-1944 · Boston, Ginn & company · leaf 286
al angles are equal. 566. How many degrees in the measure of the dihedral angle betweenthe plane of the earths equator and the ecliptic ? 567. Prove that the edge of a dihedral angle is perpendicular to theplane of the measuring angle. 568. Prove that a line and its projection on a plane determine… … Given a dihedral angle, with faces Q, B, and edge CD,bisected by plane B; P, any point in B, withPX± Q, PY±B. To prove that PX=PY. Proof. 1. Let M be the plane of PX, PF, and D its intersec-tion with CD. 2. Then vPJlft .. MA. Q. Why? 3. Similarly, M_1_ R. Why? 4. ..MA. CD. Prop. XX 5. .. CD _L DX,…
Geometry
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