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I just got an answer from my teacher. a.a is basically |a|^2

Atled wrote:

A . (A + 3B +7C) = A.A + 3(A.B) + 7(A.C)

A.B and A.C are given

A . (A + 3B +7C) = A.A +(3*3) +(7*-1)

A . (A + 3B +7C) = A.A + 2

whats A.A

X.Y = |X|*|Y| * cos(θ)

A is normal to A there for θ = 0

or

The angle between A and A is 0

cos(0) = 1

A.A = 4

A . (A + 3B +7C) = 4 + 2 =6

hope that helps

I don't understand how come A.A is 4. Is |A| = A? What logic do u use to assume them equal? Thanks.

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