Workbook workbook = new Workbook();
workbook.LoadFromFile("Equation_1.xlsx");
Worksheet sheet = workbook.Worksheets[0];
// Add a new equation at position (1, 1) with size 50x50, displaying fraction A/B
sheet.Equations.AddEquation(1, 1, 50, 50, "\\frac{A}{B}");
// Get the first equation in the worksheet
IXlsEquation equation = sheet.Equations[0];
// Update the equation content using LaTeX syntax
equation.UpdateByLatexText("\\text{tan}\\frac{\\alpha}{2}=\\frac{\\text{sin}\\alpha}{1+ \\text{cos}\\alpha}");
// Set the position and size of the equation
equation.Top = 19;
equation.Left = 72;
equation.Width = 100;
equation.Height = 100;
// Get the second equation in the worksheet
IXlsEquation equation1 = sheet.Equations[1];
// Get the collection of equation items (components of the formula)
IEquationItemCollection equationItems = equation1.EquationItems;
// Get the first item in the collection
IEquationItem item1 = equationItems[0];
item1.Text = "e-iceblue"; // Modify the text of the item
// Append a new LaTeX formula at the end
equationItems.AddByLatex("\\frac{n!}{r!(n-r)!} ");
// Insert a LaTeX formula at index 0
equationItems.InsertByLatex(0, "\\Delta A B C");
// Save the workbook
workbook.SaveToFile("out.xlsx");

HTMLOptions.Default.IsSaveFreezedPanes = true;  // true to preserve freeze panes, false to discard

sheet.Range["D7"].Formula = "=LAMBDA(val,max,IF(ISOMITTED(max),val,IF(AND(val>0,val<max),\"within range\",\"out of range\")))(A1,A2)";
                        

sheet.Range["D5"].Formula = "=LAMBDA(a,b,IF(ISOMITTED(b),a*a,a*b))(A1,A2)";