Newcomb, Simon, 1835-1909 · New York, H. Holt and company · leaf 177
to apoint on the minor axis, we conclude: Theorem XV. Either semi-axis is a mean proportionalietiveen the distances cut off from it hy a pole upon it, and lythe corresponding polar. Polar of the Focus, Substituting for {x, y) the co-or-dinates of either focus (± ae, 0) in (26), we have x= ± - TEE… … If DR is the polar of the focus F, we havea and 00 =DP OM 00- MO a _ a~ e ex but from the linear equation of the curve we have hence DP = FPFP FP and -^- = The same reasoning applies to either focus and its polar.Hence: Theorem XVI. The focal distance of any point on anellipse is in a constant…
Geometry, Analytic
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