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Show that the line through the points (1, −1, 2) (3, 4, −2) is perpendicular to the line through the points (0, 3, 2) and (3, 5, 6).

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Question

Show that the line through the points (1, −1, 2) (3, 4, −2) is perpendicular to the line through the points (0, 3, 2) and (3, 5, 6).

Sum
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Solution

Let A(1, −1, 2), B(3, 4, −2), C(0, 3, 2), D(3, 5, 6)

Direction ratio of AB = (3 − 1, 4 − (−1), −2 − 2)

= (2, 5, −4)

Direction ratio of CD = (3 − 0, 5 − 3, 6 − 2)

= (3, 2, 4)

a1a2 + b1b2 + c1c2

= 2 × 3 + 5 × 2 + (−4) × 4 

= 6 + 10 − 16

= 16 − 16

= 0

Hence, lines AB and CD are perpendicular.

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Chapter 11: Three Dimensional Geometry - Exercise 11.2 [Page 477]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 11 Three Dimensional Geometry
Exercise 11.2 | Q 2 | Page 477

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