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 79
y the general equation, when x and t/ denote theco-ordinates of the centre, is (x 7+(y—•)•=* To make the meaning ofthe equation perfectly clear,draw a circle from any pointP as centre, and with a radiuswhose length is denoted by R.Let the co-ordinates of anypoint of the circumference, asP, be x and… … Then by thehence is the central equation; and since, in general co-ordinates, PR is denoted by the difference x 74 xf, and PR by y — y, the above is THE CIRCLE. 75 the general equation. If P be taken in a different part of thecircumference, the differences x — x and y —y may become nega-tive, but…
Geometry, Analytic
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