NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 7: Coordinate Geometry - Exercise 7.2
Question 5

Question. 5

Points \(A(3,1),\ B(12,-2),\ C(0,2)\) cannot be vertices of a triangle.

Answer:

True.

Detailed Answer with Explanation:

Step 1: Three points form a triangle only if they are not collinear. If the area of the triangle formed by them is 0, then they are collinear and cannot form a triangle.

Step 2: Use the area of triangle formula for points \(A(x_1,y_1)\), \(B(x_2,y_2)\), \(C(x_3,y_3)\):

\(\text{Area} = \dfrac{1}{2}\left|x_1(y_2-y_3) + x_2(y_3-y_1) + x_3(y_1-y_2)\right|\).

Step 3: Substitute \(A(3,1)\), \(B(12,-2)\), \(C(0,2)\).

  • \(x_1=3,\ y_1=1\)
  • \(x_2=12,\ y_2=-2\)
  • \(x_3=0,\ y_3=2\)

Step 4: Compute the expression inside the absolute value:

\(x_1(y_2-y_3) = 3\big((-2)-2\big) = 3(-4) = -12\)

\(x_2(y_3-y_1) = 12\big(2-1\big) = 12(1) = 12\)

\(x_3(y_1-y_2) = 0\big(1-(-2)\big) = 0\times 3 = 0\)

Step 5: Add them:

\(-12 + 12 + 0 = 0\)

Step 6: Area of \(\triangle ABC\):

\(\text{Area} = \dfrac{1}{2}|0| = 0\)

Final Step: Since the area is 0, points A, B, and C are collinear. Therefore, they cannot be vertices of a triangle, so the statement is True.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 7: Coordinate Geometry – Exercise 7.2 | Detailed Answers