Snyder, Virgil, 1869-1950, Sisam, Charles Herschel, b. 1879 · New York : H. Holt and Company · leaf 19
Fig. 3 a. Fig. 3 6. which I meets the plane through Q perpendicular to V. Thenthe angle PQQ is a right angle. Hence, by trigonometry,we have PQ = PQ cos e. But PQ = PQ. It follows that PQ = PQ cos $. It should be observed that it makes no difference in thistheorem whether the segment PQ is positive…
Geometry, Analytic
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