Check sibling questions

Find the acute angle between the lines

(x - 4)/3 = (y + 3)/4 = (z + 1)/5 and (x - 1)/4 = (y + 1)/(-3) = (z + 10)/5


Transcript

Question 25 Find the acute angle between the lines (𝑥 − 4)/3 = (𝑦 + 3)/4 = (𝑧 + 1)/5 and (𝑥 − 1)/4 = (𝑦 + 1)/(−3) = (𝑧 + 10)/5 Angle between the pair of lines (𝑥 − 𝑥_1)/𝑎_1 = (𝑦 − 𝑦_1)/𝑏_1 = (𝑧 − 𝑧_1)/𝑐_1 and (𝑥 − 𝑥_2)/𝑎_2 = (𝑦 − 𝑦_2)/𝑏_2 = (𝑧 − 𝑧_2)/𝑐_2 is given by cos θ = |(𝑎_1 𝑎_2 + 𝑏_1 𝑏_2 + 𝑐_1 𝑐_2)/(√(〖𝑎_1〗^2 + 〖𝑏_1〗^2 + 〖𝑐_1〗^2 ) √(〖𝑎_2〗^2 + 〖𝑏_2〗^2 + 〖𝑐_2〗^2 ))| (𝒙 − 𝟒)/𝟑 = (𝒚 + 𝟑)/𝟒 = (𝒛 + 𝟏)/𝟓 Comparing with (𝑥 − 𝑥_1)/𝑎_1 = (𝑦 − 𝑦_1)/𝑏_1 = (𝑧 − 𝑧_1)/𝑐_1 𝑎1 = 3, b1 = 4, c1 = 4 (𝒙 − 𝟏)/𝟒 = (𝒚 + 𝟏)/(−𝟑) = (𝒛 + 𝟏𝟎)/𝟓 Comparing with (𝑥 − 𝑥_2)/𝑎_2 = (𝑦 − 𝑦_2)/𝑏_2 = (𝑧 − 𝑧_2)/𝑐_2 𝑎2 = 4, 𝑏2 = –3, 𝑐2 = 5 Now, cos θ = |(𝑎_1 𝑎_2 + 𝑏_1 𝑏_2 + 𝑐_1 𝑐_2)/(√(〖𝑎_1〗^2 + 〖𝑏_1〗^2 + 〖𝑐_1〗^2 ) √(〖𝑎_2〗^2 + 〖𝑏_2〗^2 + 〖𝑐_2〗^2 ))| = |(3 × 4 + 4 × (−3) + 5 × 5)/(√(3^2 + 4^2 + 5^2 ) √(4^2 +(−3)^2 + 5^2 ))| = |(12 − 12 + 25)/(√(9 + 16 + 25) √(16 + 9 + 25))| = |25/(√50 √50)| = |25/50| = |1/2| = 1/2 So, cos θ = 1/2 ∴ θ = 60° = 𝝅/𝟑 Therefore, required angle is 𝝅/𝟑 Note: Please write angle in radians and not degree

  1. Class 12
  2. Solutions of Sample Papers and Past Year Papers - for Class 12 Boards

About the Author

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo