What is the Angle Between Vectors A and C?

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SUMMARY

The discussion focuses on calculating the angle between vectors A and C, where A = 1i + 2j + 3k and B = 1i + 2k, with C being the cross product of A and B. The user initially calculated C as 4i + j - 2k and determined the angle using the dot product formula, arriving at an incorrect angle of 64.11 degrees. The correct angle is established as 90 degrees, highlighting that the cross product of two vectors is always perpendicular to the plane formed by the original vectors.

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Homework Statement


If A = 1i + 2j + 3k and B = 1i + 2k, and if C = A X B, then the angle between the vector A and the vector C is:


Homework Equations


AxB = ((a2b3-a3b2)i + (a3b1-a1b3)j + (a1b2-a2b3)k)
A·B = ABcosθ = AiBi + AjBj + AkBk


The Attempt at a Solution


I got C = 4i + j -2k and A = 1i + 2j + 3k
A·C = 4i + 2j - 6k with a magnitude of 7.48
then I used the magnitude of A and C individually to get 3.74 and 4.58 respectively.
The I used the equation cos-1(7.48/(3.74 x 4.58)) = θ
θ = 64.11 degrees. The actual answer is 90 degrees. What am I doing wrong?
 
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This is not meant to be a numerical question! Do you know what physical (spacial) property the cross product of a two vectors has with respect to the original vectors?
 
I suppose that the cross product is perpendicular to the plane of the initial vectors considering that the answer is 90 degrees. I was not fully aware of this, but if this is the case then I'll keep it in mind.
 

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