The equation of the curve for which the square of the ordinate is twic...
∵ Equation of normal at (x, y) is
Y − y = dx/dy (X − x)
Put, y = 0
Then, X = x + y dy/dx
Given, y2 = 2x X
⇒ y2 = 2x ( x + y dy/dx)
⇒ dy/dx = (y2 − 2x2)/(2xy) = ((y/x)2 − 2)/ ( 2y/x)
Put y = vx, we get dx/dy = v + x dv/dx
Then, v + x dv/dx = v2−2/2v
On integrating both sides, we get
ln (2 + v2) + ln|x| = ln c
⇒ ln (|x|(2 + v2)) = ln c
⇒ |x| ( 2 + y2/x2) = c
∵ It passes through (2, 1), then 2 (2 + 1 4 ) = c
⇒ c = 9/2
Then, |x| ( 2 + y2/x2) = 9/2
⇒ 2x2 + y2 = 9/2 |x|
⇒ 4x2 + 2y2 = 9|x|
View all questions of this test
The equation of the curve for which the square of the ordinate is twic...
Let the equation of the curve be y=f(x).
The abscissa of the point where the normal intersects the x-axis is also the x-coordinate of the point where the normal intersects the curve. Let this point be (a, 0).
We know that the equation of the normal at any point (x, y) on the curve is given by y - f(x) = f'(x)(x - x). Since the normal passes through (a, 0), we have 0 - f(a) = f'(a)(a - a).
This simplifies to -f(a) = 0, which means f(a) = 0.
Thus, the abscissa of the point where the normal intersects the x-axis is the root of the equation f(x) = 0.
Given that the square of the ordinate is twice the rectangle contained by the abscissa and the intercept of the normal on the x-axis, we have y^2 = 2(x - a)(a - 0).
Since the normal passes through (2, 1), we have 1 = f'(a)(2 - a).
Simplifying, we get f'(a) = 1/(2 - a).
To find the equation of the curve, we need to integrate f'(x) with respect to x.
Integrating f'(x) = 1/(2 - x), we get f(x) = -ln|2 - x| + C, where C is the constant of integration.
Since f(a) = 0, we have -ln|2 - a| + C = 0.
Thus, C = ln|2 - a|.
Therefore, the equation of the curve is f(x) = -ln|2 - x| + ln|2 - a|.
Simplifying, we get f(x) = ln|(2 - a)/(2 - x)|.
Therefore, the equation of the curve is y = ln|(2 - a)/(2 - x)|.
The equation of the curve for which the square of the ordinate is twic...
∵ Equation of normal at (x, y) is
Y − y = dx/dy (X − x)
Put, y = 0
Then, X = x + y dy/dx
Given, y2 = 2x X
⇒ y2 = 2x ( x + y dy/dx)
⇒ dy/dx = (y2 − 2x2)/(2xy) = ((y/x)2 − 2)/ ( 2y/x)
Put y = vx, we get dx/dy = v + x dv/dx
Then, v + x dv/dx = v2−2/2v
On integrating both sides, we get
ln (2 + v2) + ln|x| = ln c
⇒ ln (|x|(2 + v2)) = ln c
⇒ |x| ( 2 + y2/x2) = c
∵ It passes through (2, 1), then 2 (2 + 1 4 ) = c
⇒ c = 9/2
Then, |x| ( 2 + y2/x2) = 9/2
⇒ 2x2 + y2 = 9/2 |x|
⇒ 4x2 + 2y2 = 9|x|