Find the angle between the vectors A = (3, -2, 1) and B = (1, 1, 1).

Practice Questions

Q1
Find the angle between the vectors A = (3, -2, 1) and B = (1, 1, 1).
  1. 60°
  2. 45°
  3. 90°
  4. 30°

Questions & Step-by-Step Solutions

Find the angle between the vectors A = (3, -2, 1) and B = (1, 1, 1).
  • Step 1: Identify the vectors A and B. A = (3, -2, 1) and B = (1, 1, 1).
  • Step 2: Calculate the dot product A · B. This is done by multiplying the corresponding components of A and B and then adding them together: A · B = 3*1 + (-2)*1 + 1*1.
  • Step 3: Perform the calculations for the dot product: A · B = 3 - 2 + 1 = 2.
  • Step 4: Calculate the magnitude of vector A, |A|. Use the formula |A| = √(3^2 + (-2)^2 + 1^2).
  • Step 5: Perform the calculations for |A|: |A| = √(9 + 4 + 1) = √14.
  • Step 6: Calculate the magnitude of vector B, |B|. Use the formula |B| = √(1^2 + 1^2 + 1^2).
  • Step 7: Perform the calculations for |B|: |B| = √(1 + 1 + 1) = √3.
  • Step 8: Use the formula for the cosine of the angle θ: cos(θ) = (A · B) / (|A| |B|).
  • Step 9: Substitute the values into the formula: cos(θ) = 2 / (√14 * √3).
  • Step 10: To find the angle θ, use the inverse cosine function: θ = cos^(-1)(2 / (√14 * √3)).
  • Dot Product – The dot product of two vectors is calculated by multiplying their corresponding components and summing the results.
  • Magnitude of a Vector – The magnitude of a vector is found using the square root of the sum of the squares of its components.
  • Cosine of the Angle – The cosine of the angle between two vectors can be determined using the formula involving the dot product and the magnitudes of the vectors.
  • Inverse Cosine Function – To find the angle from the cosine value, the inverse cosine function (cos^(-1)) is used.
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