How can I check normal's angle?

vec_to_angle

No, dude, not that. I need to know how much is angle of normal?
Like on this picture:

The normal stands always in a right angle on the surface, that's the definition of a normal.
If you want to calculate the angle between two vectors (not ANGLEs, they must be VECTORs), use the dot product:
http://en.wikipedia.org/wiki/Dot_product
(Geometric Interpretation)

hm sinus is good to use
the side on the opposite of the angle / the lonest side
WFG Progger

Superku, that's really will be really hard for me
First, because my English is sucks...
Second, because my Mathematics skills are sucks too
May be there is an other easier way for me to do that?
Progger, what you mean by using sinus? Explain a bit more please.

Bro... just use arcsine or arccosine ((Inverse))
for example x = asinv(0.707) // x is 45
so put the lengths of the two sides u want in the parentheses..
like:
x = asinv(opposite/hypotenuse)
or if u don't have the hypotenuse then use
x = atanv(opposite/adjacent);


go to this link:
http://en.wikipedia.org/wiki/Inverse_trigonometric_functions
and go down to :Application: finding the angle of a right triangle where u will find a picture of what I am talking abt if u don't know what inverse is...

that is, in 2d space.

vec_to_angle does that for you and gives the angle of the normal on world coordinates. And the normal is always stands in 90 degrees from the surface.

I see now. Thank you bro.
But how do I calculate opposite and hypotenuse sides of the triangle?
Guys, please explain this as for a giant child, my math is really bad, I need to improve it!
Thank you for your help.

Quadraxas, sorry I missed you message.
So I need to use "vec_to_angle" then, don't I?
You are saying that normal is always stands in 90 degrees, what you mean by that?
Do you mean that normals angle is always between 0 and 90 degrees? Thank you.