Question 13 Find the equation of the normal to the curve x2 = 4y which passes through the point (1, 2).Given Curve
x2 = 4y
Differentiating w.r.t. x
2x = 4ππ¦/ππ₯
ππ¦/ππ₯ = π₯/2
β΄ Slope of normal = (β1)/(ππ¦/ππ₯) = (β1)/((π₯/2) ) = (βπ)/π
Let (h, k) be the point where normal & curve intersect
We need to find
equation of the normal to the curve x2 = 4y which passes through the point (1, 2).
But to find equation⦠we need to find point on curve
Let (h, k) be the point where normal & curve intersect
β΄ Slope of normal at (h, k) = (βπ)/π
Equation of normal passing through (h, k) with slope (β2)/β is
y β y1 = m(x β x1)
y β k = (βπ)/π (x β h)
Since normal passes through (1, 2),
it will satisfy its equation
2 β k = (β2)/β (1 β h)
k = 2 + π/π (1 β h)
Also, (h, k) lies on curve x2 = 4y
h2 = 4k
k = π^π/π
From (1) and (2)
2 + 2/β (1 β h) = β^2/4
2 + 2/β β 2 = β^2/4
2/β = β^2/4
β^3 = 8
h = ("8" )^(1/3)
h = 2
Putting h = 2 in (2)
k = β^2/4 = γ(2)γ^2/4 = 4/4 = 1
Hence, h = 2 & k = 1
Putting h = 2 & k = 1 in equation of normal
π¦βπ=(β2(π₯ β β))/β
π¦β1=(β2(π₯ β 2))/2
π¦β1=β1(π₯β2)
π¦β1=βπ₯+2
π₯+π¦=2+1
π+π=π
Made by
Davneet Singh
Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo
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