triangle in c++

September 19, 2010 at 23:14:43
Specs: Windows XP
I have classes of point,line and vector and i have to find area of triangle. anybody can help me.

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#1
September 20, 2010 at 06:05:33
IIRC, area of triangle = (0.5 * base) * height; dunno what is defined in your classes though...

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I have no aspiration for preaching. ;-)


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#2
September 20, 2010 at 06:13:45
I have Point class with members as double x,y,z; and line have Point sp1,sp2;

except this i do't have anything in my class


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#3
September 20, 2010 at 15:48:16
For area plotted as points on a graph, you can try the determinant. Not really tested as it's been a long time since I did any of this type of stuff.

typedef struct {
   double x;
   double y;
} vector;

double findDet(vector *v1, vector *v2, vector *v3) {

   double tmp = ((v1->x * pow(-1, 2)) * ((v2->y * 1) - (v3->y * 1))) +
                ((v1->y * pow(-1, 3)) * ((v2->x * 1) - (v3->x * 1))) +
                pow(-1, 4) * ((v2->x * v3->y) - (v3->x * v2->y));
                
   return (tmp != 0 ? (tmp < 0 ? tmp * -1 : tmp) : 0);            
}

...

vector pt1, pt2, pt3; // assign values first
double area = 0.5 * findDet(&pt1, &pt2, &pt3);

note that this is C and not CPP; "vector" should not be confused with cpp's vector class. I don't care much for cpp and seldom use it. :P In all honesty, I don't remember how to manipulate an object in space... that is, the z-plane. I've forgotten most of that stuff now.

Good luck. :)

-------------------------------------------
I have no aspiration for preaching. ;-)


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