The angle between two diagonals of a cube is:

The angle between two diagonals of a cube is:

• A. cos⁻¹(1/3)
• B. cos⁻¹(1/√3)
• C. sin⁻¹(1/3)
• D. 45°

Answer: A) cos⁻¹(1/3)

Explanation: Diagonals of a cube with side 'a' from origin are (a,a,a) and (−a,a,a). DRs are 1,1,1 and −1,1,1. cos θ = |−1 + 1 + 1| / (√3 * √3) = 1/3. Hence θ = cos⁻¹(1/3).