Find the angle between x + 2y + 7z + 2 = 0 and 4x + 4y + z + 2 = 0.

Category: QuestionsFind the angle between x + 2y + 7z + 2 = 0 and 4x + 4y + z + 2 = 0.
Editor">Editor Staff asked 11 months ago

Find the angle between x + 2y + 7z + 2 = 0 and 4x + 4y + z + 2 = 0.
 
(a) 69.69
 
(b) 84.32
 
(c) 63.25
 
(d) 83.25
 
I got this question in examination.
 
The doubt is from Three Dimensional Geometry topic in chapter Three Dimensional Geometry of Mathematics – Class 12
NCERT Solutions for Subject Clas 12 Math Select the correct answer from above options 
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1 Answers
Editor">Editor Staff answered 11 months ago

Correct option is (c) 63.25
 
The best I can explain: Angle between two planes cos θ=\frac {a1a2+b1b2+c1c2}{\sqrt {a1^2+b1^2+c1^2} \sqrt {a2^2+b2^2+c2^2 }}
 
cos θ = 0.45
 
θ = 63.25