Calculating Velocities After Reflection

[Sidelines]

So here's my problem... I have a particle traveling at velocity T, Vt, with components Velocity x, Velocity y, and Velocity z (3 dimensions).
This particle collides with a triangular surface. Each point of the triangle is known (x y and z for each point)
I would like to find the components of the velocity after the particle reflects off the triangle surface. (no velocity is lost so Vt remains the same)
Knowing these three points I found a vector that follows the normal angle off the surface.
You could take this vector and find the normal angle.

Known Variables:
Vt, Overall velocity
Vx, Vy, Vz, velocity components of Vt
P1, P2, P3, points of triangle (x,y,z)
Normal Vector off the surface (x,y and z components)

You could possibly find the normal angles for Z and XY, but if there's a way to do it without Sin, Cos, Tan, it would make things much easier.

Any help is appreciated as I've been stuck on this for a long time.

 

[Drakkith]

You could try the homework section. They might be able to help you there.

 

[Sidelines]

Yeah I suppose I could. This isn't for homework, but oh well

 

[Drakkith]

Yeah, I would help you if I could, but I'm still confused on why you need any more information other than the angle of impact.