Module 

Header 
/Engine/Source/Runtime/Core/Public/Math/Vector.h 
Include 
#include "Math/Vector.h" 
See if two normal vectors are coincident (nearly parallel and point in the same direction).
true if vectors are coincident (nearly parallel and point in the same direction), false otherwise.
Parameter 
Description 

Normal1 
First normalized vector. 
Normal2 
Second normalized vector. 
ParallelCosineThreshold 
Normals are coincident if dot product (cosine of angle between them) is greater than or equal to this. For example: cos(1.0 degrees). 