If the direction cosines of a line are ⟨1/c,1/c,1/c⟩, then

(a) 0<c<1                          (b) c>2

(c) c=±√2                          (d) c=±√3

[MCQ] If the direction cosines of a line are <1/c, 1/c, 1/c>, then - CBSE Class 12 Sample Paper for 2024 Boards

part 2 - Question 18 - CBSE Class 12 Sample Paper for 2024 Boards - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards - Class 12

 

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Given direction cosines of the line are 𝑙 = 1/𝑐 , m = 1/𝑐 and n = 1/𝑐 We know that 𝒍^𝟐 + 𝒎^𝟐 + 𝒏^𝟐 = 1 (1/𝑐)^2 +(1/𝑐)^2+ (1/𝑐)^2 = 1 3 (1/𝑐)^2 = 1 (𝟏/𝒄)^𝟐= 𝟏/𝟑 1/𝑐 = ±√(1/3) 1/𝑐 = ± 1/√3 c = ± √𝟑 So, the correct answer is (d)

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 15 years. He provides courses for Maths, Science and Computer Science at Teachoo