Summary of Change of Variables in Multiple Integrals

Essential Concepts

  • A transformation T is a function that transforms a region G in one plane (space) into a region R in another plane (space) by a change of variables.
  • A transformation T:GR defined as T(u,v)=(x,y) (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 f is continuous on R, then Rf(x,y)dA=Sf(g(u,v),h(u,v))(x,y)(u,v)dudv
  • If F is continuous on R, then R, 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)|dudvdw

Glossary

Jacobian
the Jacobian J(u,v) in two variables is a 2×2 determinant:
J(u,v)=|dxdudydudxdvdydv|
the Jacobian J(u,v,w) in three variables is a 3×3 determinant:
J(u,v,w)=|dxdudydudzdudxdvdydvdzdvdxdwdydwdzdw|
one-to-one transformation
a transformation T:GR defined as 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 T that transforms a region G in one plane into a region R in another plane by a change of variables
transformation
a function that transforms a region G in one plane into a region R in another plane by a change of variables