Question

Find the angle between the planes 5x + y + 3z + 1 = 0 and x + y – 2z + 6 = 0.

(a) 30.82

(b) 34.91

(c) 11.23

(d) 7.54

I got this question in my homework.

My query is from Three Dimensional Geometry in portion Three Dimensional Geometry of Mathematics – Class 12

Answer 1

The correct answer is (b) 34.91

To 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 = 0.82

θ = 34.91