Question

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

Answer 1

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