Maths > Parabola > 1.0 Conic Section

  Parabola
    1.0 Conic Section
    2.0 Parabola
    3.0 Standard equation of Parabola
    4.0 Focal distance of a point
    5.0 General equation of Parabola
    6.0 The generalized form of parabola: ${\left( {y - k} \right)^2} = 4a\left( {x - h} \right)$
    7.0 Parametric Co-ordinates
    8.0 Equation of tangent to a parabola
    9.0 Point of intersection of tangents at any two points on the parabola
    10.0 Equation of normal to the parabola
    11.0 Relation between parametric coefficients if normal meets parabola
    12.0 Important relations
    13.0 Circle through co-normal points
    14.0 Chord of contact

1.1 General Equation of Conic Section

As shown in figure $2$, let us assume the coordinates of focus is $S(\alpha ,\beta )$ and the equation of directrix is $ax + by + c = 0$, then the equation of conic section whose eccentricity is $e$ can be find out using the formulae $$SP = e \times PM$$


Using distance formulae, we get $$\sqrt {{{\left( {x - \alpha } \right)}^2} + {{\left( {y - \beta } \right)}^2}} = e \times \frac{{\left| {ax + by + c} \right|}}{{\sqrt {{a^2} + {b^2}} }}$$

Squaring both sides, we get $${\left( {x - \alpha } \right)^2} + {\left( {y - \beta } \right)^2} = {e^2} \times \frac{{{{(\left| {ax + by + c} \right|)}^2}}}{{{a^2} + {b^2}}}$$

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