A treatise on special or elementary geometry (1877)
Olney, Edward, 1827-1887, Olney, Edward, 1827-1887. Elements of trigonometry, plane and spherical · New York : Sheldon · leaf 201
are paral-lel {405), and hence the anglethus formed (S-EDF) will be a triedral supplemental to S-ABC {433\ andthe facial angles of the two having their edges parallel will be equal {416), andconsequently the triedrals equal {437)- Now, SE being perpendicular to ASB,and SF to ASC, angle ESF is… … Fig. 280. OF TEIEDRALS. 181 of the diedrals of S-ABC. We are now to show that the facial angles ofS-ABC are supplements of the diedrals of S-EDF; i. s., that ASB is the sup-plement of D-SE-F, BSC of E-SD-F, and ASC of D-SF-E. Since SE is by hy-pothesis perpendicular to ASB, it is perpendicular to…
Geometry · Trigonometry
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