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MathematicsParabolaTangent to ParabolaHard2 minPYQ_2018
MathematicsHardsingle choice

Tangent and normal are drawn atP16,16on the parabolay2=16x, which intersect the axis of the parabola atA &B, respectively. IfCis the center of the circle through the pointsP, A &BandCPB=θ,then a value oftanθis:

Question diagram: Tangent and normal are drawn at P 16 , 16 on the parabola y

Options:

Answer:
C
Solution:



Equation of tangent at x1,y1 is  yy1=2ax+x1

Equation of normal at x1,y1 is y-y1=-y12a(x-x1)

Here tangent and normal passes through P(16,16)

Equation of tangent is 2y=x+16

Equation of normal is y+2x=48

Tangent and normal intersect x-axis at A-16,0 and B(24,0)

Since, APB is a right angled triangle, hence AB is the diameter for the circle.

Also mid point of AB is center of the circle.

Hence Centre =4,0

Slope of PC =43

Slope of PB=-2

tanθ=43+21-2×43=10-5=2

Stream:JEESubject:MathematicsTopic:ParabolaSubtopic:Tangent to Parabola
2mℹ️ Source: PYQ_2018

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