point (k,k) lies on parabola

so k²=4ak

so k=4a

the equation of normal to parabola at (4a,4a) in point form is

y-4a=-4a(x-4a)/2a

y=-2x+12a is equation of normal

now we will find the point at which normal cuts parabola again by using this

that point comes(9a,+-6a)

m=slope of line joining focus and point is

4a-a/4a-0

=3/4

slope of line joining other point(9a,+-6a)is +-3/4

so m_1.m₂=-1

which gives 90 degree

or use angle formula

we get Tan@=7/24

check the figure

Hope u got it

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