Summary of Change of Variables in Multiple Integrals

Essential Concepts

  • A transformation TT is a function that transforms a region GG in one plane (space) into a region RR in another plane (space) by a change of variables.
  • A transformation T:GRT:GR defined as T(u,v)=(x,y)T(u,v)=(x,y) (or T(u,v,w)=(x,y,z))((or T(u,v,w)=(x,y,z))( is said to be a one-to-one transformation if no two points map to the same image point.
  • If ff is continuous on RR, then Rf(x,y)dA=Sf(g(u,v),h(u,v))(x,y)(u,v)dudvRf(x,y)dA=Sf(g(u,v),h(u,v))(x,y)(u,v)dudv
  • If FF is continuous on RR, then RR, then RF(x,y,z)dV=GF(g(u,v,w),h(u,v,w),k(u,v,w))(x,y,z)(u,v,w)dudvdw=GH(u,v,w)|J(u,v,w)|dudvdwRF(x,y,z)dV=GF(g(u,v,w),h(u,v,w),k(u,v,w))(x,y,z)(u,v,w)dudvdw=GH(u,v,w)|J(u,v,w)|dudvdw

Glossary

Jacobian
the Jacobian J(u,v)J(u,v) in two variables is a 2×22×2 determinant:
J(u,v)=|dxdudydudxdvdydv|J(u,v)=∣ ∣dxdudydudxdvdydv∣ ∣
the Jacobian J(u,v,w)J(u,v,w) in three variables is a 3×33×3 determinant:
J(u,v,w)=|dxdudydudzdudxdvdydvdzdvdxdwdydwdzdw|J(u,v,w)=∣ ∣ ∣ ∣dxdudydudzdudxdvdydvdzdvdxdwdydwdzdw∣ ∣ ∣ ∣
one-to-one transformation
a transformation T:GRT:GR defined as T(u,v)=(x,y)T(u,v)=(x,y) is said to be one-to-one if no two points map to the same image point
planar transformation
a function TT that transforms a region GG in one plane into a region RR in another plane by a change of variables
transformation
a function that transforms a region GG in one plane into a region RR in another plane by a change of variables