Flag Analytical Geometry> For what values of `a` will the tangents ...
question mark

For what values of `a` will the tangents to the parabola y^2=4ax from a point, not on the y axis ,will be normal to x^2=4y

Shuvajyoti Ghosh , 8 Years ago
Grade 12th pass
anser 1 Answers
Vikas TU

Last Activity: 8 Years ago

Differntiate and put y also,
 y^2=4ax
ydy/dx = 2a
root(ax)dy/dx = a
dy/dx = a/root(ax) = > root(a/x).....................(1)
 
Differntiate same as
x^2 = 4ay
2x =4dy/dx
x = 2dy/dx
dy/dx = x/2
normal will be:
x/2 * n = -1
n = -2/x …...............(2)
 
eqn. (1)  and eqn. (2) are equal.
 
therfore,
 
-2/x = root(a/x)
squaring both sides,
4/x^2 = a/x
4/x^2 – a/x = 0
(4 – ax)/x^2 = 0
x cannot be zero
or
4 – ax = 0
ax = 4
x = 4/a
y = 4/a^2
put these x and y in y^2 = 4ax
u will get,
a^4 = 1
(a^2 + 1) (a^2-1) = 0
a^2 = 1
a = 1  and a = -1

Provide a better Answer & Earn Cool Goodies

star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments


Ask a Doubt

Get your questions answered by the expert for free