What is the angle between the vectors (1, 2, 2) and (2, 1, 2)?

Practice Questions

Q1
What is the angle between the vectors (1, 2, 2) and (2, 1, 2)?
  1. 90 degrees
  2. 60 degrees
  3. 45 degrees
  4. 30 degrees

Questions & Step-by-Step Solutions

What is the angle between the vectors (1, 2, 2) and (2, 1, 2)?
  • Step 1: Identify the vectors. We have vector u = (1, 2, 2) and vector v = (2, 1, 2).
  • Step 2: Calculate the dot product of the vectors u and v. The dot product is calculated as u · v = (1*2) + (2*1) + (2*2).
  • Step 3: Perform the multiplication: (1*2) = 2, (2*1) = 2, and (2*2) = 4. Now add them together: 2 + 2 + 4 = 8. So, u · v = 8.
  • Step 4: Calculate the magnitude of vector u. The magnitude |u| is calculated as √(1^2 + 2^2 + 2^2).
  • Step 5: Perform the calculations: 1^2 = 1, 2^2 = 4, and 2^2 = 4. Now add them: 1 + 4 + 4 = 9. So, |u| = √9 = 3.
  • Step 6: Calculate the magnitude of vector v. The magnitude |v| is calculated as √(2^2 + 1^2 + 2^2).
  • Step 7: Perform the calculations: 2^2 = 4, 1^2 = 1, and 2^2 = 4. Now add them: 4 + 1 + 4 = 9. So, |v| = √9 = 3.
  • Step 8: Use the cosine formula to find the cosine of the angle θ: cos(θ) = (u · v) / (|u| |v|).
  • Step 9: Substitute the values: cos(θ) = 8 / (3 * 3) = 8 / 9.
  • Step 10: Use the inverse cosine function to find θ: θ = cos⁻¹(8/9).
  • Step 11: Calculate θ to find that it is approximately 60 degrees.
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