Derivation of the Vector Dot Product and the Vector Cross Product

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Derivation of the Vector Dot Product and the Vector Cross Product

description

Derivation of the Vector Dot Product and the Vector Cross Product. Derivation of the Vector Dot Product. u·v =∑ i u i v i = ∑ i u i e i ∑ i v j e j. (u 1 e 1 + u 2 e 2 + u 3 e 3 ) (v 1 e 1 + v 2 e 2 + v 3 e 3 ). Kronecker Delta e i ·e j = δ ij = 1 when i = j - PowerPoint PPT Presentation

Transcript of Derivation of the Vector Dot Product and the Vector Cross Product

Derivation of the Vector Dot Product and the Vector Cross

Product

Derivation of the Vector Dot Product

u·v =∑i ui vi

= ∑i ui ei ∑i vj ej

(u1 e1 + u2 e2

+ u3 e3) (v1 e1 + v2 e2

+ v3

e3)

Kronecker Delta ei·ej = δij = 1 when i = j

0 when i ≠ j

= u1v1e1e1+ u2v2e2e2+u3v3e3e3

= u1v1+ u2v2+u3v3

Vector Cross Product Einstein Notation

u × υ = εijk e i uj υk  

= Σijkεijkeiujυk

= Σi Σj Σk εijkeiujυk

Levi-Civati Symbol

ε =

0 unless i, j, k are distinct

+1 if i, j, k is an even permutation of (1, 2, 3)

-1 if i. j, k is an odd permutation of (1, 2, 3)

Derivation of the Cross Product

Levi-Civati Symbol

3 1 3 1 2 2

even 123, 231, 312 odd 321, 213, 132

Derivation of the Cross Product

= (ε123 u2v3+ ε132u3v2) e1 + (ε213 u1v3 + ε231 u3v1) e2+ (ε312 u1v2 + ε321 u2v1) e3 

= (u2v3 – u3v2)e1 + (u1v3 – u3v1)e2 + (u1v2 – u2v1)e3