An elementary treatise on analytical geometry : embracing plane co-ordinate geometry, and an introduction to geometry of three dimensions (1869)
Johnson, William Woolsey, 1841-1927 · Philadelphia : J.B. Lippincott · leaf 86
easured in different directions, and/ is negative.When the pole is at the centre, d = 0 and e = 0, the positive andnegative values of r become equal to radius, and/= — R2; hencer = ± R. 113. A more useful formof the polar equation maybe found, thus: Let r re-present the distance of thecentre from… … The three lines r, r and R form the sides of a triangle of which6 is an angle. Hence the equation expresses that the square ofone side of a triangle equals the sum of the squares of the other twosides, minus twice their product, into the cosine of the includedangle. D* 82 THE CIRCLE. If the centre…
Geometry, Analytic
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