判断一个点是否在圆上，圆内，圆外，用c++写这个程序

#include <stdio.h>
#include <math.h>

int main() {
  // 假设圆心为 (0, 0)，半径为 r
  float x, y, r, dist;

  printf("请输入点的 x 坐标：");
  scanf("%f", &x);

  printf("请输入点的 y 坐标：");
  scanf("%f", &y);

  printf("请输入圆的半径：");
  scanf("%f", &r);

  // 计算点到圆心的距离
  dist = sqrt(x * x + y * y);

  if (dist == r) {
    printf("该点在圆上\n");
  } else if (dist < r) {
    printf("该点在圆内\n");
  } else {
    printf("该点在圆外\n");
  }

  return 0;
}

注意：本程序假设圆心坐标为 (0, 0)，如果圆心不是 (0, 0)，需要在计算点到圆心的距离时将圆心坐标减去。

相关问题

NX二次开发C++ 代码判断圆柱面是内圆还是外圆

以下是用 C++ 实现判断圆柱面是内圆还是外圆的代码：

#include <iostream>
#include <cmath>
#include <vector>
#include <NXOpen/NXException.hxx>
#include <NXOpen/Part.hxx>
#include <NXOpen/PartCollection.hxx>
#include <NXOpen/Features_Feature.hxx>
#include <NXOpen/Features_FeatureCollection.hxx>
#include <NXOpen/Features_CircularPatternBuilder.hxx>
#include <NXOpen/Features_CircularPattern.hxx>
#include <NXOpen/Features_FeatureUtilities.hxx>
#include <NXOpen/Annotations_Dimension.hxx>
#include <NXOpen/Annotations_DimensionCollection.hxx>
#include <NXOpen/Annotations_DimensionValue.hxx>
#include <NXOpen/Annotations_DimensionValueCollection.hxx>
#include <NXOpen/Annotations_DimensionValueType.hxx>
#include <NXOpen/Annotations_ImplicitView.hxx>
#include <NXOpen/Annotations_Annotation.hxx>
#include <NXOpen/Annotations_AnnotationCollection.hxx>
#include <NXOpen/Annotations_Text.hxx>
#include <NXOpen/Annotations_TextCollection.hxx>
#include <NXOpen/Annotations_Arrow.hxx>
#include <NXOpen/Annotations_ArrowCollection.hxx>
#include <NXOpen/Annotations_Leader.hxx>
#include <NXOpen/Annotations_LeaderCollection.hxx>
#include <NXOpen/Annotations_LeaderArrow.hxx>
#include <NXOpen/Annotations_LeaderArrowCollection.hxx>
#include <NXOpen/Annotations_Line.hxx>
#include <NXOpen/Annotations_LineCollection.hxx>
#include <NXOpen/Annotations_Arc.hxx>
#include <NXOpen/Annotations_ArcCollection.hxx>
#include <NXOpen/Annotations_Ellipse.hxx>
#include <NXOpen/Annotations_EllipseCollection.hxx>
#include <NXOpen/Annotations_Spline.hxx>
#include <NXOpen/Annotations_SplineCollection.hxx>
#include <NXOpen/Annotations_HoleNote.hxx>
#include <NXOpen/Annotations_HoleNoteCollection.hxx>
#include <NXOpen/Annotations_Symbol.hxx>
#include <NXOpen/Annotations_SymbolCollection.hxx>
#include <NXOpen/Geom_Curve.hxx>
#include <NXOpen/Geom_CurveCollection.hxx>
#include <NXOpen/Geom_Arc.hxx>
#include <NXOpen/Geom_ArcCollection.hxx>
#include <NXOpen/Geom_Circle.hxx>
#include <NXOpen/Geom_CircleCollection.hxx>
#include <NXOpen/Geom_Line.hxx>
#include <NXOpen/Geom_LineCollection.hxx>
#include <NXOpen/Geom_Conic.hxx>
#include <NXOpen/Geom_ConicCollection.hxx>
#include <NXOpen/Geom_Spline.hxx>
#include <NXOpen/Geom_SplineCollection.hxx>
#include <NXOpen/Geom_BSplineCurve.hxx>
#include <NXOpen/Geom_BSplineCurveCollection.hxx>
#include <NXOpen/Geom_Surface.hxx>
#include <NXOpen/Geom_SurfaceCollection.hxx>
#include <NXOpen/Geom_Plane.hxx>
#include <NXOpen/Geom_PlaneCollection.hxx>
#include <NXOpen/Geom_Cylinder.hxx>
#include <NXOpen/Geom_CylinderCollection.hxx>

using namespace std;
using namespace NXOpen;

bool IsInnerCircle(CartesianPoint center, Vector3d normal, CartesianPoint point);

int main(int argc, char *argv[])
{
    Part *part = NULL;
    try
    {
        // 获取当前工作部件
        Part *part = Part::GetSession()->Parts()->Work();
        if (part == NULL)
        {
            cerr << "当前没有打开的部件，请先打开一个部件！" << endl;
            return -1;
        }

        // 选取一个圆柱面特征
        Features::Feature *feat = NULL;
        feat = part->Features()->FindObject("CYLINDER");
        if (feat == NULL)
        {
            cerr << "当前部件中没有找到圆柱面特征！" << endl;
            return -1;
        }

        // 获取圆柱面的参数
        Geom::Cylinder *cylinder = dynamic_cast<Geom::Cylinder *>(feat->Geometry());
        if (cylinder == NULL)
        {
            cerr << "获取圆柱面参数失败！" << endl;
            return -1;
        }

        // 获取圆柱面的圆心坐标和法向量
        CartesianPoint center = cylinder->CenterPoint();
        Vector3d normal = cylinder->AxisVector();

        // 构造一个测试点
        CartesianPoint testPoint;
        testPoint.X = center.X + 10;
        testPoint.Y = center.Y;
        testPoint.Z = center.Z;

        // 判断测试点是否在内圆上
        if (IsInnerCircle(center, normal, testPoint))
        {
            cout << "测试点在圆柱面内部的圆上！" << endl;
        }
        else
        {
            cout << "测试点在圆柱面外部的圆上！" << endl;
        }

        return 0;
    }
    catch (const NXException &ex)
    {
        cerr << "程序异常退出：" << ex.Message() << endl;
        if (part != NULL)
        {
            delete part;
        }
        return -1;
    }
}

bool IsInnerCircle(CartesianPoint center, Vector3d normal, CartesianPoint point)
{
    // 计算点到圆心的向量
    Vector3d vec;
    vec.X = point.X - center.X;
    vec.Y = point.Y - center.Y;
    vec.Z = point.Z - center.Z;

    // 计算法向量与点到圆心向量的夹角
    double angle = acos((vec.X * normal.X + vec.Y * normal.Y + vec.Z * normal.Z) /
                        (sqrt(vec.X * vec.X + vec.Y * vec.Y + vec.Z * vec.Z) * sqrt(normal.X * normal.X + normal.Y * normal.Y + normal.Z * normal.Z)));

    // 判断是否在内圆上
    if (angle < M_PI / 2)
    {
        return true;
    }
    else
    {
        return false;
    }
}

以上代码中，IsInnerCircle() 函数用于判断一个点是否在圆柱面的内圆上，其中 center、normal 和 point 都是 NXOpen 中的 CartesianPoint 和 Vector3d 类型，分别表示圆柱面的圆心坐标、法向量和测试点的坐标。如果该函数返回 true，则表示测试点在圆柱面的内圆上；否则，表示测试点在圆柱面的外圆上。

用C++ 编写程序，已知平面上有一个圆，圆心坐标为(4, 6)，半径为2。请输入一个点M的坐标(x, y)，判断点M是在圆内、圆上还是在圆外。

可以使用以下代码来判断点M的位置：

#include <stdio.h>
#include <math.h>

int main()
{
double x, y, distance;
printf("请输入点M的坐标(x, y)：");
scanf("%lf %lf", &x, &y);
distance = sqrt(pow(x - 4, 2) + pow(y - 6, 2));
if (distance < 2)
{
printf("点M在圆内\n");
}
else if (distance == 2)
{
printf("点M在圆上\n");
}
else
{
printf("点M在圆外\n");
}
return 0;
}

注意：这段代码只能判断点M与圆心的距离，而不能判断点M是否在圆的边界上。如果需要判断点M是否在圆的边界上，需要对判断条件进行修改。