Finding the Angle Between Vectors A & B

AI Thread Summary
Vectors A and B both have a magnitude of 5.12, and their sum equals the vector 6.37j. The cosine law is being used to determine the angle between the two vectors, but initial calculations yielded incorrect results of 103 degrees and 77 degrees. The user suggests verifying the numbers used in the calculations, as their attempts to apply the cosine formula did not yield the expected angle. The discussion highlights confusion over the correct method and results for finding the angle between the vectors.
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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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