The angle between two planes with normals n₁ and n₂ is given by

Question

Accepted Answer

C. cos θ = n₁ · n₂ / (|n₁||n₂|)

1. The angle between two planes equals the angle between their normals.
2. Use the dot-product formula for angle between vectors.
3. cos θ = (n₁ · n₂) / (|n₁| · |n₂|).
4. Distractors confuse sin/cos or replace the dot product with magnitudes.
_Source: syllabus Maths Part 2 Ch 11 "Three Dimensional Geometry", §11.8_

Answer

sin θ = n₁ · n₂ / (|n₁||n₂|)

Answer

cos θ = |n₁| · |n₂|

Answer

tan θ = n₁ × n₂

The angle between two planes with normals n₁ and n₂ is given by

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