Module 

Header 
/Engine/Source/Runtime/Core/Public/Math/Matrix.h 
Include 
#include "Math/Matrix.h" 
Source 
/Engine/Source/Runtime/Core/Public/Math/Matrix.inl 
Transform a direction vector by the inverse of this matrix  will not take into account translation part. If you want to transform a surface normal (or plane) and correctly account for nonuniform scaling you should use TransformByUsingAdjointT with adjoint of matrix inverse.
Faster version of InverseTransformVector that assumes no scaling. WARNING: Will NOT work correctly if there is scaling in the matrix.