如何在opengl中绘制给定起点的圆弧？

#include <GL/glut.h>
#include <cmath>

void drawArc(float cx, float cy, float r, float startAngle, float endAngle) {
    glBegin(GL_LINE_STRIP);
    for (float theta = startAngle; theta <= endAngle; theta += 0.01) {
        float x = cx + r * cos(theta);
        float y = cy + r * sin(theta);
        glVertex2f(x, y);
    }
    glEnd();
}

void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    
    // 绘制圆弧，起点(100, 100)，半径50，起始角度30度，结束角度150度
    drawArc(100, 100, 50, 30 * 3.14159 / 180, 150 * 3.14159 / 180);
    
    glFlush();
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(400, 400);
    glutCreateWindow("OpenGL Arc");
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, 400.0, 0.0, 400.0);
    glutDisplayFunc(display);
    glutMainLoop();
    
    return 0;
}