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Cheatography

Algebra and Geometry - Class 27 Cheat Sheet (DRAFT) by

Contents: Axler 1-6 (no 6C, no 5) Berberian 7-8

This is a draft cheat sheet. It is a work in progress and is not finished yet.

SECTION 1

C, Fields, Lists, Fn, Vector Spaces

Definition of complex numbers (n∈­C)

C = { a+bi : a,b ∈ R }
addition in C (a+bi) + (c+di) = (a+c) + (b+d)i
multip­lic­ation in C (a+bi)­(c+di) = (ac-bd) + (ad+bc)i

Properties of Fields

commut­ativity a+b = b+a ∧ ab = ba ∀a,b ∈ F
associ­ativity (a+b)+c = a+(b+c) ∧ (ab)c = a(bc) ∀a,b,c ∈ F
identities c+0 = c ∧ 1c = c ∀c ∈ F
additive inverse ∀a ∈ F ∃b ∈ F : a+b = 0
multip­lic­ative inverse a ∈ F, a ≠ 0, ∃b ∈ F : a+b = 0
distri­butive property c(a+b) = ca + cb ∀a,b,c ∈ F

Definition of list L with length n

n∈N, L : { 1,2,…,n } → Elements
L = (x1,...,xn)

Definition of Fn

Fn = { (x1,...,xn) : xjF for j = 1,...,n}
addition in Fn (x1,...,xn) + (y1,...,yn) = (x1+y1,...,xn+yn)
zero vector 0 = (0,...,0)
additive inverse For xFn, -xFn = (-x1,...,-xn)
scalar multip­lic­ation in Fn c ∈ F, c(x1,...,xn) = (cx1,...,cxn)
 

Definition of addition and scalar multip­lic­ation

addition on a set V + : (u,vV) → u +v
scalar multip­lic­ation on a set V * : (c ∈ F, vV) → cv

Defintion of Vector Space

Vector Space = V + (+) + (*)
commut­ativity u+v = v+u
associ­ativity (u+v)+w = u+(v+w) ∧ (ab)v = a(bv)
additive identity0V : v+0 = v
additive inversevV, ∃wV : v+w = 0
multip­lic­ative identity 1v = v
distri­butive property a(v+w) = av + aw ∀a ∈ F
vV = vector ∨ point