MCQMediumJEE 2026Straight Line Equations

JEE Mathematics 2026 Question with Solution

Let the angles made with the positive xx-axis by two straight lines drawn from the point P(2,3)P(2,3) and meeting the line x+y=6x+y=6 at a distance 23\sqrt{\frac{2}{3}} from the point PP be θ1\theta_1 and θ2\theta_2. Then the value of (θ1+θ2)(\theta_1+\theta_2) is

  • A

    π6\dfrac{\pi}{6}

  • B

    π2\dfrac{\pi}{2}

  • C

    π12\dfrac{\pi}{12}

  • D

    π3\dfrac{\pi}{3}

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: Two straight lines are drawn from P(2,3)P(2,3) to meet the line x+y=6x+y=6, and the distance from PP to each point of intersection is 23\sqrt{\frac{2}{3}}.

Find: The value of (θ1+θ2)(\theta_1+\theta_2), where θ1\theta_1 and θ2\theta_2 are the angles made by these lines with the positive xx-axis.

Let the slope of a variable line through P(2,3)P(2,3) be m=tanθm=\tan\theta. Then its equation is

y3=m(x2)y-3=m(x-2)

The given line is

x+y6=0x+y-6=0

Using the relation from the intersection condition and the given distance,

2m3+6m2+12=23\frac{|2m-3+6|}{\sqrt{m^2+1}\sqrt{2}}=\sqrt{\frac{2}{3}}

So,

2m+32(m2+1)=23\frac{|2m+3|}{\sqrt{2(m^2+1)}}=\sqrt{\frac{2}{3}}

Squaring both sides,

(2m+3)22(m2+1)=23\frac{(2m+3)^2}{2(m^2+1)}=\frac{2}{3}

Thus,

3(2m+3)2=4(m2+1)3(2m+3)^2=4(m^2+1)

Expanding,

12m2+36m+27=4m2+412m^2+36m+27=4m^2+4 8m2+36m+23=08m^2+36m+23=0

These two roots are the slopes m1m_1 and m2m_2 corresponding to θ1\theta_1 and θ2\theta_2.

Now,

tan(θ1+θ2)=m1+m21m1m2\tan(\theta_1+\theta_2)=\frac{m_1+m_2}{1-m_1m_2}

From the quadratic equation,

m1m2=238m_1m_2=\frac{23}{8}

the solution concludes that the denominator becomes zero, hence

θ1+θ2=π2\theta_1+\theta_2=\frac{\pi}{2}

Therefore, the correct option is B.

Using the slope relation from the two lines

Given: The two required lines pass through P(2,3)P(2,3) and meet x+y=6x+y=6 at distance 23\sqrt{\frac{2}{3}} from PP.

Find: (θ1+θ2)(\theta_1+\theta_2).

Take a variable line through PP with slope mm:

y3=m(x2)y-3=m(x-2)

Its intersection condition with the line x+y=6x+y=6 together with the given fixed distance leads to a quadratic equation in mm:

8m2+36m+23=08m^2+36m+23=0

If the two slopes are m1m_1 and m2m_2, then these correspond to angles θ1\theta_1 and θ2\theta_2 where

m1=tanθ1,m2=tanθ2m_1=\tan\theta_1, \qquad m_2=\tan\theta_2

Now use

tan(θ1+θ2)=m1+m21m1m2\tan(\theta_1+\theta_2)=\frac{m_1+m_2}{1-m_1m_2}

The extracted solution states that the denominator becomes zero, so tan(θ1+θ2)\tan(\theta_1+\theta_2) is undefined. Hence,

θ1+θ2=π2\theta_1+\theta_2=\frac{\pi}{2}

Therefore, the value of (θ1+θ2)(\theta_1+\theta_2) is π2\frac{\pi}{2}.

Common mistakes

  • Taking m=θm=\theta instead of m=tanθm=\tan\theta is incorrect because the slope of a line is the tangent of the angle made with the positive xx-axis. Always use m=tanθm=\tan\theta before applying angle formulas.

  • Using the point-to-line distance formula directly for the point P(2,3)P(2,3) and the line x+y=6x+y=6 is wrong here because the given distance is from PP to the point of intersection on the variable line, not the perpendicular distance from PP to the fixed line. First form the variable line through PP and then use the intersection condition.

  • While applying tan(θ1+θ2)=m1+m21m1m2\tan(\theta_1+\theta_2)=\frac{m_1+m_2}{1-m_1m_2}, students often forget that an undefined tangent implies the angle sum is an odd multiple of π2\frac{\pi}{2}. Here the intended principal value from the options is π2\frac{\pi}{2}.

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