Michael would like to build a fence around his paddock. The diagram is not to scale.
5
4
X
V
Find a simplified expression for the perimeter of his paddock.

Step-by-step explanation:

The angle between the planes is the same as the angle between their normal vectors, which are

n₁ = ⟨1, 1, 1⟩

n₂ = ⟨4, 3, 1⟩

The angle θ between the vectors is such that

⟨1, 1, 1⟩ • ⟨4, 3, 1⟩ = ||⟨1, 1, 1⟩|| ||⟨4, 3, 1⟩|| cos(θ)

Solve for cos(θ) :

4 + 3 + 1 = √(1² + 1² + 1²) √(4² + 3² + 1²) cos(θ)

8 = √3 √26 cos(θ)

cos(θ) = 8/√78