Pedro Machado Manhães de Castro a écrit :

> The answer is no.

No, the answer to the first question is yes. RTFM:

http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Kernel_23_ref/Class_Circle_2.htmlAs for the relative position of a segment wrt a circle, there are more cases to

distinguish, and you may need to do something along the lines of what Pedro suggests.

See squared_distance(), between the center and the segment and/or the endpoints

or the supporting line.

http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Kernel_23_ref/Function_squared_distance.html> However:

>

> You could do that by:

>

> Check whether the supporting line of your segment and the circle

> intersect (with do_intersect). If it does not intersect, then the

> segment is completely outside or inside the circle (if it does interest

> you, you can find which of those two cases are applied by checking

> whether one end point is inside the circle or not). Otherwise, you check

> whether the squared_distance between the center and the supporting line

> is equal to the squared_radius of the circle or not. If yes, then you

> project the center onto the supporting line of the segment and check if

> the segment contains that point (with Has_on_2) (I am assuming that a

> 'tangent segment' is the one such that its supporting line is tangent to

> the circle + the segment intersects the circle). And now, if the

> distance is not equal to the radius, check whether both end points of

> the segment are outside/on the circle or not (so you are able to decide

> whether it divides or not the circle).

>

> Search the manual index for Has_on_2, Do_intersect_2,

> Has_on_bounded_side_2, Intersect_2 and squared_distance.

>

> Cheers,

> Pedro Machado

>

> On Wed, Nov 12, 2008 at 8:22 PM, Emerson Carride <

[hidden email]
> <mailto:

[hidden email]>> wrote:

>

> In CGAL has a function that returns if a given point is inside or

> outside or in boundary of a circle.

>

> I want to know if CGAL has a function that returns if a given

> segment is tangent to a circle or divided the circle into two parts?

>

>

>

>

> --

> Emerson Amade Carride

> Matemática Aplicada e Computação Científica

> Instituto de Ciências Matemáticas e Computação

> USP - São Carlos

> tel: (16) 3411 0877; (11) 4538 3315 ; cel: (11) 71289888

>

>

--

Sylvain Pion

INRIA Sophia-Antipolis

Geometrica Project-Team

CGAL,

http://cgal.org/--

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