Sigma Percentile
JEE Advanced 1986
LEVELBoard

Animated Solution for Mathematics - Straight Lines: The points and are vertices of

Select Answer:

Visualized Solution

Identify the Given Points

  • Let the three given points be:
  • Point
  • Point
  • Point

The Triangle Trap

  • Before calculating side lengths, we must check if a triangle is even formed.
  • If the points are collinear (lying on the same straight line), they cannot form a triangle.
  • The area of the triangle formed by collinear points is .

The Slope Tool for Collinearity

  • To check for collinearity, we compare the slopes of the segments.
  • If , then points , , and are collinear.
  • Slope formula:

Raw Setup: Slope of

  • Let's set up the slope for points and :

Atomic Compute: Slope of

  • Simplify the numerator:
  • Simplify the denominator:
  • Thus,

Raw Setup: Slope of

  • Let's set up the slope for points and :

Atomic Compute: Slope of

  • Simplify the numerator and denominator:
  • Divide both by :

Conclusion: Collinear Points

  • Since :
  • The points , , and lie on the same straight line.
  • Therefore, they cannot form a triangle.
  • Correct Option: none of these

The Sigma Insight: Slope of a Line

Analyzing the Setup

We are given three points: , , and . The objective is to identify the nature of the triangle formed by these vertices.
While the instinct to calculate side lengths using the distance formula is strong, this approach is often a trap in competitive examinations. We must first investigate whether these points actually form a triangle or if they are collinear.

The Trap of Assumption

If three points are collinear, they lie on a single straight line. In such a case, the area of the triangle they would "form" is exactly .
To determine if these points are collinear, we do not need the distance formula. Instead, we use the concept of the slope, which represents the constant steepness of a line.

The Slope

Your Most Elegant Weapon
The slope between two points and is defined by the ratio of the vertical rise to the horizontal run:
If the slope of segment is equal to the slope of segment , the points , , and must lie on the same line.

The Calculation

A Dance of Numbers
First, we calculate the slope for segment :
Simplifying the numerator, we have . Thus, the slope is:
Next, we calculate the slope for segment :
Reducing the fraction by dividing both the numerator and denominator by , we obtain:

The Revelation

Since , the slopes are identical. This confirms that the points , , and are perfectly collinear.
Because these points lie on the same straight line, they cannot form a triangle. Given the standard options for such a problem, the correct conclusion is none of these.

Similar Questions

JEE Advanced 1979
LEVELBoard

The points and are:

(A)
Collinear
(B)
Vertices of a parallelogram
(C)
Vertices of a rectangle
(D)
None of these
JEE Advanced 2002
LEVELJEE Main

Let be fixed angle. If and , then is obtained from by

(A)
clockwise rotation around origin through an angle
(B)
anticlockwise rotation around origin through an angle
(C)
reflection in the line through origin with slope
(D)
reflection in the line through origin with slope
JEE Main 2003
LEVELJEE Main

A body travels a distance s in t seconds. It starts from rest and ends at rest. In the first part of the journey, it moves with constant acceleration f and in the second part with constant retardation r. The value of t is given by

(A)
(B)
(C)
(D)