Change of Variables in Multivariable Calculus: Jacobian and Mappings, Study notes of Mathematics

Lecture notes on the change of variables technique in multivariable calculus. It covers the transformation of coordinates, focusing on the jacobian determinant and its role in calculating areas under mappings. The notes include examples of linear and non-linear mappings, such as polar coordinates, and demonstrate how to find the image of geometric shapes under these transformations. The document also explains how to compute the jacobian determinant for linear maps and its relation to the area of parallelograms, offering a comprehensive overview of the topic for students studying multivariable calculus. It is useful for understanding coordinate transformations and their applications in integration and area calculations. (438 characters)

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2024/2025

Uploaded on 06/06/2025

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bg1
Lectures changeofilariables
gSince we missed aclass we are skipping
The phrase change of variables means
changing coordinates Here we will learn
why dA dxdy rdrd
dV dxdydz rolzdrolf
psinddpolbd0MITEE.lt
we will consider maps
i.e functions GDIR on adomain D
RWe will denote points in Das nu
and points in Bas xyGCD
pf3
pf4
pf5

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Lectures

changeofilariables g

Since we^ missed^ a^ class^ we^ are^

skipping The phrase change^ of (^) variables means changing coordinates Here we^ will^ learn

why

dA dxdy rdrd dV dxdydz rolzdrolf psinddpolbd 0 MITEE.lt we (^) will consider

maps

i.e (^) functions G (^) D IR (^) on a (^) domain D R We will denote

points

in (^) D as nu and (^) points in^ B^ as^ x^ y GCD

So x u^ v y you^ v (^) Glu 4 x^ use y u (^) D Example We (^) have alreadysecretly^ been thinking about this^ Consider G (^) 0,0 (^) 0,2 7 R G r^ rcos (^) rsin This is^ the^ map that^ translates polar cords into (^) rectangular coordinates Another (^) classic type of

mapping

linearnaps G u v^ AU Cv^ But (^) Dv A^ B^ C^ D^ constant

Note

If

you

have taken linear^ algebra notice we^ can describe 6 with^ a (^) matrix B 5 Y^ E

Fact

Linear mappings send straight lines (^) to straight lines parallel lines to^ parallel lines

We have uv y ux a G c^ x^ Cv^ ex^ x

y

So (^) x CV (^1) V So y CV c^ E

ly

Elsinayoff

Glu c^ UC^ uc^ x^ y UC (^) U (^) XC y

UC XC C^ XC

y xc since^ us0 xoo b

i

iii

Hence (^) the image of 1,2 1,2^ consists^ of x y such^ that y x y 4x or in^ other words

KXy

(^4 1 )

Inverse

UV U XV

y UV xx (^) v V2^ v V (^) E since^11 So (^) u xv (^) xFE P So G^ x^

y

u x^ y Cx

y F F Leachantoramapping

The

Jacindetrminant (^) of G u^ v^ u^ v^ y

u v is

sacco 3 1 This is^ often^ denoted Note Jac^

G is^ a^

function (^) of a v Then The^ Jacobian

of

a linear

map

Gcu x (^) Au Cv But^ Dv (^) is (^) constant with value JacCO AD^ BC^ B 5 And (^) for any domain^ D area GCD^ Jac^ G (^) area D