Sign in
Please select an account to continue using cracku.in
↓ →
Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
If a line L is perpendicular to the line $$5x - y = 1$$, and the area of the triangle formed by the line L and the coordinate axes is 5 sq units, then the distance of the line L from the line $$x + 5y = 0$$ is:
First, we need to find the slope of the given line $$5x - y = 1$$. To do this, we rearrange it into slope-intercept form $$y = mx + c$$.
Starting with $$5x - y = 1$$:
Subtract $$5x$$ from both sides: $$-y = -5x + 1$$
Multiply both sides by $$-1$$: $$y = 5x - 1$$
So, the slope of this line is 5.
Since line L is perpendicular to this line, the product of their slopes must be $$-1$$. Let the slope of L be $$m$$. Then:
$$m \times 5 = -1$$
Solving for $$m$$: $$m = -\frac{1}{5}$$
Thus, the slope of line L is $$-\frac{1}{5}$$.
The equation of line L can be written as $$y = -\frac{1}{5}x + b$$, where $$b$$ is the y-intercept. To avoid fractions, multiply through by 5:
$$5y = -x + 5b$$
Rearrange to standard form: $$x + 5y = 5b$$
Let $$c = 5b$$, so the equation becomes:
$$x + 5y = c$$ (1)
Now, we find the intercepts of line L with the coordinate axes to use the area condition.
When $$x = 0$$: $$5y = c$$ $$\Rightarrow$$ $$y = \frac{c}{5}$$ (y-intercept)
When $$y = 0$$: $$x = c$$ (x-intercept)
The area of the triangle formed with the axes is given as 5 sq units. The area formula is $$\frac{1}{2} \times |\text{x-intercept}| \times |\text{y-intercept}|$$. Since area is positive, we use absolute values:
$$\frac{1}{2} \times |c| \times \left|\frac{c}{5}\right| = 5$$
Since $$\left|\frac{c}{5}\right| = \frac{|c|}{5}$$, this becomes:
$$\frac{1}{2} \times |c| \times \frac{|c|}{5} = 5$$
Simplify: $$\frac{1}{2} \times \frac{|c|^2}{5} = 5$$
Because $$|c|^2 = c^2$$, we have:
$$\frac{c^2}{10} = 5$$
Multiply both sides by 10: $$c^2 = 50$$
Take square roots: $$c = \sqrt{50}$$ or $$c = -\sqrt{50}$$
Simplify: $$c = 5\sqrt{2}$$ or $$c = -5\sqrt{2}$$
So, the possible equations for line L are:
$$x + 5y = 5\sqrt{2}$$ or $$x + 5y = -5\sqrt{2}$$
Now, we need to find the distance from line L to the line $$x + 5y = 0$$.
Write both lines in the form $$ax + by + k = 0$$:
The reference line is $$x + 5y = 0$$, so $$x + 5y + 0 = 0$$.
For the first case, $$x + 5y - 5\sqrt{2} = 0$$.
For the second case, $$x + 5y + 5\sqrt{2} = 0$$ (since $$x + 5y = -5\sqrt{2}$$ implies $$x + 5y + 5\sqrt{2} = 0$$).
The distance $$d$$ between two parallel lines $$ax + by + c_1 = 0$$ and $$ax + by + c_2 = 0$$ is:
$$d = \frac{|c_1 - c_2|}{\sqrt{a^2 + b^2}}$$
Here, $$a = 1$$, $$b = 5$$, so $$\sqrt{a^2 + b^2} = \sqrt{1^2 + 5^2} = \sqrt{26}$$.
For the first line L: $$x + 5y - 5\sqrt{2} = 0$$, so $$c_1 = -5\sqrt{2}$$. The reference line has $$c_2 = 0$$.
Distance: $$d_1 = \frac{|-5\sqrt{2} - 0|}{\sqrt{26}} = \frac{5\sqrt{2}}{\sqrt{26}}$$
For the second line L: $$x + 5y + 5\sqrt{2} = 0$$, so $$c_1 = 5\sqrt{2}$$.
Distance: $$d_2 = \frac{|5\sqrt{2} - 0|}{\sqrt{26}} = \frac{5\sqrt{2}}{\sqrt{26}}$$
Both distances are the same. Simplify:
$$\frac{5\sqrt{2}}{\sqrt{26}} = 5 \sqrt{\frac{2}{26}} = 5 \sqrt{\frac{1}{13}} = \frac{5}{\sqrt{13}}$$
Alternatively, $$\frac{5\sqrt{2}}{\sqrt{26}} = \frac{5\sqrt{2}}{\sqrt{2 \times 13}} = \frac{5\sqrt{2}}{\sqrt{2} \times \sqrt{13}} = \frac{5}{\sqrt{13}}$$
So, the distance is $$\frac{5}{\sqrt{13}}$$ units.
Comparing with the options:
A. $$\frac{7}{\sqrt{13}}$$
B. $$\frac{7}{\sqrt{5}}$$
C. $$\frac{5}{\sqrt{13}}$$
D. $$\frac{5}{\sqrt{7}}$$
Hence, the correct answer is Option C.
Create a FREE account and get:
Predict your JEE Main percentile, rank & performance in seconds
Educational materials for JEE preparation
Ask our AI anything
AI can make mistakes. Please verify important information.
AI can make mistakes. Please verify important information.