Ошибки компиляции "Обращение к переменной как к функции"

//---------------------------------------------------------------------------
 
#include <vcl.h>
#pragma hdrstop
#include "math.h"
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
class GraphicClass
 {
 private:
 int sin, cos, tan;
 int xmax, ymax;
 int xmid, ymid;
 int XKind, YKind;
 double X, Y;
 double deltaX, deltaY;
 double a_x, b_x, c_x, a_y, b_y, c_y;
 public:
 GraphicClass();
 void DrawAxis();
 void DrawGraphic();
 void SetXKind(int xkind);
 void SetYKind(int ykind);
 void SetAX(double ax);
 void SetBX(double bx);
 void SetCX(double cx);
 void SetAY(double ay);
 void SetBY(double by);
 void SetCY(double cy);
 void SetDeltaX(double dX);
 void SetDeltaY(double dY);
 };
GraphicClass::GraphicClass()
 {
 xmax = 681;
 ymax = 465;
 xmid = xmax / 2;
 ymid = ymax / 2;
 deltaX = 10;
 deltaY = 10;
 a_x = 1;
 b_x = 1;
 c_x = 0;
 a_y = 1;
 b_y = 1;
 c_y = 0;
 XKind = 0;
 YKind = 0;
 }
void GraphicClass::DrawAxis()
 {
 Form1 -> PaintBox1 -> Repaint();
 Form1 -> PaintBox1 -> Canvas -> MoveTo(1, ymid);
 Form1 -> PaintBox1 -> Canvas -> LineTo(xmax, ymid);
 Form1 -> PaintBox1 -> Canvas -> MoveTo(xmid, 1);
 Form1 -> PaintBox1 -> Canvas -> LineTo(xmid, ymax);
 
 for (int i = 0; i <= xmax / deltaX; i++)
  {
  Form1 -> PaintBox1 -> Canvas -> MoveTo(xmid + i * deltaX, ymid - 1);
  Form1 -> PaintBox1 -> Canvas -> LineTo(xmid + i * deltaX, ymid + 2);
  Form1 -> PaintBox1 -> Canvas -> MoveTo(xmid - i * deltaX, ymid - 1);
  Form1 -> PaintBox1 -> Canvas -> LineTo(xmid - i * deltaX, ymid + 2);
  }
 for (int i = 0; i <= ymax / deltaY; i++)
  {
  Form1 -> PaintBox1 -> Canvas -> MoveTo(xmid - 1, ymid + i * deltaY);
  Form1 -> PaintBox1 -> Canvas -> LineTo(xmid + 2, ymid + i * deltaY);
  Form1 -> PaintBox1 -> Canvas -> MoveTo(xmid - 1, ymid - i * deltaY);
  Form1 -> PaintBox1 -> Canvas -> LineTo(xmid + 2, ymid - i * deltaY);
  }
 }
void GraphicClass::DrawGraphic()
 {
 for (int t = -1000; t <= 1000; t++)
  {
  switch(XKind)
   {
   case 0: X = a_x; break;
   case 1: X = a_x * 0.01 * t + b_x; break;
   case 2: if (!(b_x < 0 && t == 0))
    X = a_x * (pow(0.01 * t, b_x) + c_x); break;
   case 3: X = a_x * sin(b_x * 0.01 * t + c_x); break;
   case 4: X = a_x * cos(b_x * 0.01 * t + c_x); break;
   case 5: X = a_x * tan(b_x * 0.01 * t + c_x); break;
   case 6: if (b_x * 0.01 * t + c_x != 0)
    X = a_x / tan(b_x * 0.01 * t + c_x); break;
   case 7: X = a_x * exp(b_x * 0.01 * t + c_x); break;
   case 8: X = a_x * sin(b_x * 0.01 * t) * sin(c_x * 0.01 * t); break;
   case 9: X = a_x * sin(b_x * 0.01 * t) * cos(c_x * 0.01 * t); break;
   case 10: X = a_x * cos(b_x * 0.01 * t) * cos(c_x * 0.01 * t); break;
   case 11: X = a_x * exp(b_x * 0.01 * t) * sin (c_x * 0.01 * t); break;
   };
  switch(YKind)
   {
   case 0: Y = a_y; break;
   case 1: Y = a_y * 0.01 * t + b_y; break;
   case 2: if (!(b_y < 0 && t == 0))
    Y = a_y * (pow(0.01 * t, b_y) + c_y); break;
   case 3: Y = a_y * sin(b_y * 0.01 * t + c_y); break;
   case 4: Y = a_y * cos(b_y * 0.01 * t + c_y); break;
   case 5: Y = a_y * tan(b_y * 0.01 * t + c_y); break;
   case 6: if (b_y * 0.01 * t + c_y != 0)
    Y = a_y / tan(b_y * 0.01 * t + c_y); break;
   case 7: Y = a_y * exp(b_y * 0.01 * t + c_y); break;
   case 8: Y = a_y * sin(b_y * 0.01 * t) * sin(c_y * 0.01 * t); break;
   case 9: Y = a_y * sin(b_y * 0.01 * t) * cos(c_y * 0.01 * t); break;
   case 10: Y = a_y * cos(b_y * 0.01 * t) * cos(c_y * 0.01 * t); break;
   case 11: Y = a_y * exp(b_y * 0.01 * t) * sin (c_y * 0.01 * t); break;
   };
  Form1 -> PaintBox1 -> Canvas -> Pixels[xmid + X * deltaX][ymid - Y * deltaY] = clGreen;
  }
 }
void GraphicClass::SetXKind(int xkind)
 {
 XKind = xkind;
 }
void GraphicClass::SetYKind(int ykind)
 {
 YKind = ykind;
 }
void GraphicClass::SetAX(double ax)
 {
 a_x = ax;
 }
void GraphicClass::SetBX(double bx)
 {
 b_x = bx;
 }
void GraphicClass::SetCX(double cx)
 {
 c_x = cx;
 }
void GraphicClass::SetAY(double ay)
 {
 a_y = ay;
 }
void GraphicClass::SetBY(double by)
 {
 b_y = by;
 }
void GraphicClass::SetCY(double cy)
 {
 c_y = cy;
 }
void GraphicClass::SetDeltaX(double dX)
 {
 deltaX = dX;
 }
void GraphicClass::SetDeltaY(double dY)
 {
 deltaY = dY;
 }
 
GraphicClass Graphic;
//--------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
Graphic.DrawAxis();
}
//--------------------------------------------------------------------
void __fastcall TForm1::TrackBar1Change(TObject *Sender)
{
Edit7 -> Text = TrackBar1 -> Position;
Graphic.SetDeltaX(TrackBar1 -> Position);
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::TrackBar2Change(TObject *Sender)
{
Edit8 -> Text = TrackBar2 -> Position;
Graphic.SetDeltaY(TrackBar2 -> Position);
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::ComboBox1Change(TObject *Sender)
{
Graphic.SetXKind(ComboBox1 -> ItemIndex);
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::ComboBox2Change(TObject *Sender)
{
Graphic.SetYKind(ComboBox2 -> ItemIndex);
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit1Change(TObject *Sender)
{
if (Edit1 -> Text == "") Edit1 -> Text = "0";
Graphic.SetAX(Edit1 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit2Change(TObject *Sender)
{
if (Edit2 -> Text == "") Edit2 -> Text = "0";
Graphic.SetBX(Edit2 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit3Change(TObject *Sender)
{
if (Edit3 -> Text == "") Edit3 -> Text = "0";
Graphic.SetCX(Edit3 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit4Change(TObject *Sender)
{
if (Edit4 -> Text == "") Edit4 -> Text = "0";
Graphic.SetAY(Edit4 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit5Change(TObject *Sender)
{
if (Edit5 -> Text == "") Edit5 -> Text = "0";
Graphic.SetBY(Edit5 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}
//--------------------------------------------------------------------
void __fastcall TForm1::Edit6Change(TObject *Sender)
{
if (Edit6 -> Text == "") Edit6 -> Text = "0";
Graphic.SetCY(Edit6 -> Text.ToDouble());
Graphic.DrawAxis();
Graphic.DrawGraphic();
}