Can you prove the formula for projection of a vector using dot products?

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SUMMARY

The formula for the projection of a vector \( \text{proj}_{v}u \) onto another vector \( v \) is confirmed to be true, specifically that \( (\text{proj}_{v}u) \cdot (u - \text{proj}_{v}u) = 0 \). This indicates that the projection is orthogonal to the residual vector \( u - \text{proj}_{v}u \). To prove this in \( \mathbb{R}^n \), one must express \( \text{proj}_{v}u \) using dot products, which clarifies the relationship between the vectors involved.

PREREQUISITES
  • Understanding of vector projections in linear algebra
  • Familiarity with dot product operations
  • Knowledge of vector spaces, particularly \( \mathbb{R}^n \)
  • Basic proof techniques in mathematics
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  • Study the derivation of the projection formula \( \text{proj}_{v}u = \frac{u \cdot v}{v \cdot v} v \)
  • Learn about orthogonality in vector spaces
  • Explore the properties of dot products and their geometric interpretations
  • Practice proving vector identities using algebraic manipulation
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Students of mathematics, particularly those studying linear algebra, educators teaching vector projections, and anyone interested in the geometric interpretation of vector operations.

Bipolarity
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Is the following statement true? My intuition tells me it is true, but I have been trying to prove it, without much success:

[tex](proj_{v}u ) \cdot (u - proj_{v}u) = 0[/tex]

It makes complete since if you draw it out in R2, but I am trying to prove it in Rn.

Any ideas?

BiP
 
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The formula is true. To prove it, can you find another way to write [itex]proj_vu[/itex]?? Try to write it with dot products.
 

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