Module 

Header 
/Engine/Source/Runtime/Core/Public/Math/Vector.h 
Include 
#include "Math/Vector.h" 
See if two normal vectors are nearly orthogonal (perpendicular), meaning the angle between them is close to 90 degrees.
true if vectors are orthogonal (perpendicular), false otherwise.
Parameter 
Description 

Normal1 
First normalized vector. 
Normal2 
Second normalized vector. 
OrthogonalCosineThreshold 
Normals are orthogonal if absolute value of dot product (cosine of angle between them) is less than or equal to this. For example: cos(89.0 degrees). 