The line has equation . The plane has equation . Find the acute angle between and .

Answer and explanation

Correct answer: A.

  1. Step 1: The acute angle between a line with direction and a plane with normal satisfies .
  2. Step 2: Calculate the scalar product: . The magnitudes are and . Thus .
Answer
.
Why not the others: The inverse cosine computes the angle between the line and the normal vector rather than the plane; the fraction miscalculates the dot product by adding all terms; the value does not match the scalar product.

Practise more Vectors in 3D Space and Complex Numbers.

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