Maths > Parabola > 10.0 Equation of normal to the parabola

  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

10.2 Slope form

Let the equation of parabola be ${y^2} = 4ax$ and slope of normal $m$ at a point $P({x_1},{y_1})$ is $\frac{{ - {y_1}}}{{2a}}$ i.e.,


$$m = \frac{{ - {y_1}}}{{2a}}$$ or, $${y_1} = - 2am$$

Put the value of ${y_1}$ in the equation of parabola, we get $${x_1} = a{m^2}$$

The equation of normal to the parabola is $$y - {y_1} = m\left( {x - {x_1}} \right)$$ $$y + 2am = m\left( {x - a{m^2}} \right)$$ $$y = mx - 2am - a{m^3}$$

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