If A = 2i + 3j and B = 3i + 4j, find the angle between A and B.

Practice Questions

Q1
If A = 2i + 3j and B = 3i + 4j, find the angle between A and B.
  1. 45 degrees
  2. 60 degrees
  3. 30 degrees
  4. 90 degrees

Questions & Step-by-Step Solutions

If A = 2i + 3j and B = 3i + 4j, find the angle between A and B.
  • Step 1: Identify the vectors A and B. A = 2i + 3j and B = 3i + 4j.
  • Step 2: Calculate the dot product A · B. This is done by multiplying the corresponding components: (2 * 3) + (3 * 4) = 6 + 12 = 18.
  • Step 3: Calculate the magnitude of vector A. |A| = √(2^2 + 3^2) = √(4 + 9) = √13.
  • Step 4: Calculate the magnitude of vector B. |B| = √(3^2 + 4^2) = √(9 + 16) = √25 = 5.
  • Step 5: Use the formula for the cosine of the angle θ: cos(θ) = (A · B) / (|A||B|). Substitute the values: cos(θ) = 18 / (√13 * 5).
  • Step 6: Calculate the value of cos(θ). This gives cos(θ) = 18 / (√13 * 5) = 0.6.
  • Step 7: Find the angle θ by taking the inverse cosine: θ = cos⁻¹(0.6). This results in θ = 60 degrees.
  • Dot Product – The dot product of two vectors is used to find the cosine of the angle between them.
  • Magnitude of Vectors – Calculating the magnitude of vectors A and B is essential for finding the angle between them.
  • Trigonometric Functions – Understanding how to use the cosine function to find angles from the dot product.
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