How to calculate Angle between vectors

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Discussion Overview

The discussion revolves around calculating the angle between vectors, specifically focusing on force vectors represented in a diagram. Participants explore methods for determining angles between these vectors and their relationship to a central vector.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to calculate the angle between two force vectors and their angle with a central vector, mentioning normalization and the use of sin-1 for angle determination.
  • Another participant emphasizes the need for the vectors to be in a calculable form to compute angles, questioning how the vectors are provided beyond a visual representation.
  • A later reply suggests using the dot product and cross product formulas to calculate the angle between two vectors, presenting both methods as valid options.

Areas of Agreement / Disagreement

Participants express different perspectives on the requirements for calculating angles, with some focusing on the need for specific vector representations while others propose mathematical methods without resolving the overall approach.

Contextual Notes

There is uncertainty regarding the exact representation of the vectors and how they can be normalized for calculation. The discussion does not clarify the assumptions needed for the proposed methods.

IMK
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Hello,
In attached image the three black lines represent three force vectors x,y,z of some arbitrary magnitude, these I can normalize and by taking the sin-1 I get there effect angle. What I would like to calculate is the angle between any two of the black line axies thus theta xy = ?. also I would like to calculate the angle between any of the x,y,z axies and the and the central red vector.

Many thanks in advance IMK
 

Attachments

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In order to "calculate" the angle (as opposed to measuring it) you have to be "given" the vectors in some "calculable" form. How you would then calculate the angle depends on how you are given the vectors. How are you given x, y, and z, other than just a drawing?
 
HallsofIvy said:
In order to "calculate" the angle (as opposed to measuring it) you have to be "given" the vectors in some "calculable" form. How you would then calculate the angle depends on how you are given the vectors. How are you given x, y, and z, other than just a drawing?

These would be force vectors that I would normalize to be in the range of 0 to 1
Many thanks in advance IMK
 
[tex]\vec{A}\cdot\vec{B}= \|\vec{A}\|\|\vec{B}\|\cos{\theta}[/tex] and
[tex]\|\vec{A}\times\vec{B}\|=\|\vec{A}\|\vec{B}\|\sin{\theta}[/tex]. You can use either of these to calculate the angle.
 
nicksauce said:
[tex]\vec{A}\cdot\vec{B}= \|\vec{A}\|\|\vec{B}\|\cos{\theta}[/tex] and
[tex]\|\vec{A}\times\vec{B}\|=\|\vec{A}\|\vec{B}\|\sin{\theta}[/tex]. You can use either of these to calculate the angle.
Many thanks!
 

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