NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 7: Coordinate Geometry
Exercise 7.4

Coordinate geometry applications: special triangles, parallelogram properties, section formula, centroid, loci, and distance computations.

Question. 1

If \((-4,\,3)\) and \((4,\,3)\) are two vertices of an equilateral triangle, find the coordinates of the third vertex, given that the origin lies in the interior of the triangle.

Answer:

The third vertex is \(\bigl(0,\;3-4\sqrt{3}\bigr).\)

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Question. 2

\(A(6,1),\ B(8,2)\) and \(C(9,4)\) are three vertices of a parallelogram \(ABCD\). If \(E\) is the midpoint of \(DC\), find the area of \(\triangle ADE\).

Answer:

Area \(= \dfrac{3}{4}\) square units.

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Question. 3

The points \(A(x_1,y_1),\ B(x_2,y_2)\) and \(C(x_3,y_3)\) are the vertices of \(\triangle ABC\).

(i) The median from \(A\) meets \(BC\) at \(D\). Find \(D\).

(ii) Find the point \(P\) on \(AD\) such that \(AP:PD=2:1\).

(iii) Find points \(Q\) and \(R\) on medians \(BE\) and \(CF\) respectively such that \(BQ:QE=2:1\) and \(CR:RF=2:1\).

(iv) Hence, write the coordinates of the centroid of \(\triangle ABC\).

Answer:

(i) \(D\bigl(\dfrac{x_2+x_3}{2},\;\dfrac{y_2+y_3}{2}\bigr)\).

(ii) \(P\bigl(\dfrac{x_1+x_2+x_3}{3},\;\dfrac{y_1+y_2+y_3}{3}\bigr)\).

(iii) \(Q\) and \(R\) are also \(\bigl(\dfrac{x_1+x_2+x_3}{3},\;\dfrac{y_1+y_2+y_3}{3}\bigr)\).

(iv) Centroid \(G\bigl(\dfrac{x_1+x_2+x_3}{3},\;\dfrac{y_1+y_2+y_3}{3}\bigr)\).

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Question. 4

The points \(A(1,-2),\ B(2,3),\ C(a,2)\) and \(D(-4,-3)\) form a parallelogram. Find \(a\) and the height of the parallelogram taking \(AB\) as the base.

Answer:

\(a=-3\) and the height (on base \(AB\)) is \(\dfrac{24}{\sqrt{26}}\).

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Question. 5

Students stand on a grid for drill. Points \(A, B, C, D\) are shown below. Is it possible to place Jaspal so that he is equidistant from all four? If yes, give his position.

Fig. 7.4 (grid with A, B, C, D)

(Use grid coordinates: \(A(3,5),\ B(6,8),\ C(10,5),\ D(7,1)\).)

Answer:

Yes. Jaspal should stand at \(\bigl(6.5,\,4.5\bigr)\).

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Question. 6

Ayush travels House \(\to\) Bank \(\to\) School \(\to\) Office along straight segments instead of going directly House \(\to\) Office. If \(H(2,4),\ B(5,8),\ S(13,14),\ O(13,26)\), find the extra distance travelled.

Answer:

Extra distance \(= 27 - \sqrt{605}\;\text{km} \approx 2.404\;\text{km}.\)

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NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 7: Coordinate Geometry – Exercise 7.4 | Detailed Answers