Let the angles made with the positive -axis by two straight lines drawn from the point and meeting the line at a distance from the point be and . Then the value of is
- A
- B
- C
- D
Let the angles made with the positive -axis by two straight lines drawn from the point and meeting the line at a distance from the point be and . Then the value of is
Correct answer:B
Standard Method
Given: Two straight lines are drawn from to meet the line , and the distance from to each point of intersection is .
Find: The value of , where and are the angles made by these lines with the positive -axis.
Let the slope of a variable line through be . Then its equation is
The given line is
Using the relation from the intersection condition and the given distance,
So,
Squaring both sides,
Thus,
Expanding,
These two roots are the slopes and corresponding to and .
Now,
From the quadratic equation,
the solution concludes that the denominator becomes zero, hence
Therefore, the correct option is B.
Using the slope relation from the two lines
Given: The two required lines pass through and meet at distance from .
Find: .
Take a variable line through with slope :
Its intersection condition with the line together with the given fixed distance leads to a quadratic equation in :
If the two slopes are and , then these correspond to angles and where
Now use
The extracted solution states that the denominator becomes zero, so is undefined. Hence,
Therefore, the value of is .
Taking instead of is incorrect because the slope of a line is the tangent of the angle made with the positive -axis. Always use before applying angle formulas.
Using the point-to-line distance formula directly for the point and the line is wrong here because the given distance is from to the point of intersection on the variable line, not the perpendicular distance from to the fixed line. First form the variable line through and then use the intersection condition.
While applying , students often forget that an undefined tangent implies the angle sum is an odd multiple of . Here the intended principal value from the options is .
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