Geo5.1.1

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Write the equation of the parabola whose focus is (1,2) and directrix is x+1=0\,

Given S=(1,2) and l=x+1=0\,

Let P(x,y) be any point on the parabola.

SP^{{2}}=PM^{{2}}\,

(x-1)^{2}+(y-2)^{2}=[{\frac  {x+1}{{\sqrt  {1}}}}]^{2}\,

(y-2)^{2}=(x+1)^{2}-(x-1)^{2}\,

Therefore,the equation of the parabola is

(y-2)^{2}=4x\,


Main Page:Geometry:The Parabola