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Verify the following: (–1, 2, 1), (1, –2, 5), (4, –7, 8) and (2, –3, 4) are the vertices of a parallelogram. - Mathematics

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Question

Verify the following:

(–1, 2, 1), (1, –2, 5), (4, –7, 8) and (2, –3, 4) are the vertices of a parallelogram.

Sum

Solution

Let the vertices of quadrilateral ABCD be A(−1, 2, 1), B(1, –2, 5), C(4, –7, 8) and D(2, –3, 4), then

AB2 = `sqrt((1 + 1)^2 + (−2 - 2)^2 + (5 - 1)^2)`

= `sqrt(4 + 16 + 16)`

= `sqrt36`

= 6

BC2 = `sqrt((4 - 1)^2+ (-7 + 2)^2 + (8 - 5)^2)`

= `sqrt(9 + 25 + 9)`

= `sqrt43`

CD2 = `sqrt((2 - 4)^2 + (−3 + 7)^2 + (4 - 8)^2)`

= `sqrt(4 + 16 + 16)`

= `sqrt36`

= 6

AD2 = `sqrt((2 + 1)^2 + (−3 - 2)^2 + (4 - 1)^2)`

= `sqrt(9 + 25 + 9)`

= `sqrt43`

AB2 = CD2 and BC2 = AD2

AB = CD and BC = AD

Hence, the given points are the vertices of a parallelogram.

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Chapter 12: Introduction to Three Dimensional Geometry - Exercise 12.2 [Page 273]

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NCERT Mathematics [English] Class 11
Chapter 12 Introduction to Three Dimensional Geometry
Exercise 12.2 | Q 3.3 | Page 273

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