Tangents to Curve $$y = \int\limits_0^x {|t|dt}$$

The intercepts on x-axis made by tangents to the curve, , which are parallel to the line y = 2x, are equal to:

(1)         (2)         (3)         (4)

[JEE Main 2013]

Solution

If x > 0,

Slope of tangent =

Since the tangent is parallel to the line y = 2x whose slope = 2,

So, the point of contact is (2, 2) and the equation of the tangent is,

y – 2 = 2(x – 2)

Or, y = 2x – 2 whose intercept on the x-axis is 1.

If x < 0,

Slope of tangent =

Since the tangent is parallel to the line y = 2x whose slope = 2,

or x = -2

So, the point of contact is (-2, -2) and the equation of the tangent is,

y + 2 = 2(x + 2)

Or, y = 2x + 2 whose intercept on the x-axis is -1. Hence, option (1).

pdf Download

Leave a Reply