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Angles between normals at 2 points on a surface

  1. Jan 19, 2012 #1
    I have been reading about the normal vector to a point on a surface.


    Can anyone explain if I have normals to 2 points on a surface and I want to compute the inclinations between them, how would one proceed?
  2. jcsd
  3. Jan 19, 2012 #2


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    Hey svishal03.

    What do you mean by inclinations? Do you mean the angle between them?
  4. Jan 20, 2012 #3


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    How you determine the angle between normals depends upon the way the surface is given. For example, if you are given f(x,y,z)= constant, the normals at [itex](x_0, y_0, z_0)[/itex] and [itex](x_1, y_1, z_1)[/itex] are given by [itex]\nabla f(x_0, y_0, z_0)[/itex] and [itex]\nabla f(x_1, y_1, z_1)[/itex]. And, of course, the angle between those two vectors is given by their dot product: [itex]cos^{-1}(\vec{u}\cdot\vec{v}/|\vec{u}||\vec{v}|)[/itex].
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