Finding the Angle Between Vectors A & B

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SUMMARY

The discussion centers on calculating the angle between two vectors A and B, both with magnitudes of 5.12, given that their sum equals the vector 6.37j. The cosine law was applied incorrectly, leading to an erroneous angle of 103 degrees. The correct angle, as confirmed by multiple participants, is approximately 77 degrees. Participants emphasized the importance of verifying calculations and understanding vector addition principles.

PREREQUISITES
  • Understanding of vector addition and representation
  • Familiarity with the cosine law in trigonometry
  • Basic knowledge of angles and their measurement
  • Ability to perform algebraic manipulations and solve equations
NEXT STEPS
  • Review the cosine law and its application in vector calculations
  • Study vector addition and its geometric interpretations
  • Practice solving problems involving angles between vectors
  • Explore the concept of unit vectors and their role in vector analysis
USEFUL FOR

Students in physics or mathematics, educators teaching vector concepts, and anyone seeking to improve their understanding of trigonometric applications in vector analysis.

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Homework Statement



Vectors A and B have equal magnitudes of 5.12. If the sum of A and B is the vector 6.37j, determine the angle between A and B.

Homework Equations



Cosine law?

The Attempt at a Solution



I attempted to do this using the cosine law which I thought made sense but 103 degrees is not the right answer..
 
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when i use the cosine equation:
cosA = (b^2 +c^2 - a^2)/2bc
A = cos-1[(b^2 +c^2 - a^2)/2bc]
i did not get 103 degrees... id suggest to check your numbers??
 
You got 77 degrees correct?
I just subtracted from 180 because the angle I assume is tail to tail.

I also tried 77 degrees (or rather 76.9 degrees) and it's also not the answer.
 

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