मराठी

Draw a quadrilateral in the Cartesian plane, whose vertices are (–4, 5), (0, 7), (5, –5) and (–4, –2). Also, find its area.

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प्रश्न

Draw a quadrilateral in the Cartesian plane, whose vertices are (–4, 5), (0, 7), (5, –5) and (–4, –2). Also, find its area.

बेरीज
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उत्तर

Let ABCD be the given quadrilateral with vertices A (–4, 5), B (0, 7), C (5, –5), and D (–4, –2).

Then, by plotting A, B, C, and D on the Cartesian plane and joining AB, BC, CD, and DA, the given quadrilateral can be drawn as

To find the area of quadrilateral ABCD, we draw one diagonal, say AC.

Accordingly, area (ABCD) = area (ΔABC) + area (ΔACD)

We know that the area of a triangle whose vertices are (x1, y1), (x2, y2), and (x3, y3) is 

`1/2 |x_1 (y_2 - y_3) + x_2 (y_3 - y_1) + x_3 (y_1 - y_2)|`

Therefore, area of ΔABC

= `1/2 |-4 (7 + 5) + 0 (-5 -5) +5 (5 - 7)| "unit"^2`

= `1/2 |-4 (12) + 5 (-2)| "unit"^2`

= `1/2 |-48 - 10| "unit"^2`

= `1/2 |-58| "unit"^2`

= `1/2 xx 58  "unit"^2`

= 29 unit2

Area of ΔACD

= `1/2 |-4 (-5 + 2) + 5 (-2 -5) + (-4) (5 + 5)| "unit"^2`

= `1/2 |-4 (-3) + 5 (-7) -4 (10)| "unit"^2`

= `1/2 |12 - 35 - 40| "unit"^2`

= = `1/2 |-63| "unit"^2`

= `63/2 "unit"^2`

Thus, area (ABCD) = `29 + 63/2 "unit"^2 = (58 + 63)/2 "unit"^2 = (121)/2 "unit"^2`

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पाठ 9: Straight Lines - EXERCISE 9.1 [पृष्ठ १५८]

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एनसीईआरटी Mathematics [English] Class 11
पाठ 9 Straight Lines
EXERCISE 9.1 | Q 1. | पृष्ठ १५८

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