怎么将文本框tEdit的Text属性赋值给一个float的变量，用atof

void __fastcall TForm1::Button1Click(TObject *Sender)
{
double k,s;
float a=atof(Edit1->Text);
int b=atoi(Edit2->Text);
float c=atof(Edit3->Text);
s=a/2/tan(b/2*3.1415926/180);
k=s+c;
}