MainWindow.xaml

<Window x:Class="WpfLatexCalculator.MainWindow"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
      xmlns:local="clr-namespace:WpfLatexCalculator"
      xmlns:wpfMath="clr-namespace:WpfMath.Controls;assembly=WpfMath"
      mc:Ignorable="d"
      Title="WPF LaTeX Calculator" Height="NaN" Width="324" d:DesignHeight="476.96">
    <Window.Resources>
        <Style TargetType="Button">
            <Setter Property="Margin" Value="2"/>
            <Setter Property="FontSize" Value="16"/>
            <Setter Property="MinHeight" Value="40"/>
        </Style>
        <Style x:Key="OperatorButton" TargetType="Button" BasedOn="{StaticResource {x:Type Button}}">
            <Setter Property="Background" Value="LightGray"/>
        </Style>
        <Style x:Key="FunctionButton" TargetType="Button" BasedOn="{StaticResource {x:Type Button}}">
            <Setter Property="Background" Value="LightSkyBlue"/>
        </Style>
    </Window.Resources>
    <Grid Margin="10">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Border Grid.Row="0" BorderBrush="Gray" BorderThickness="1" MinHeight="60" Margin="0,0,0,5" Padding="5">
            <wpfMath:FormulaControl x:Name="ExpressionDisplay" Formula="" VerticalAlignment="Center" Scale="20" />
        </Border>

        <Border Grid.Row="1" BorderBrush="Gray" BorderThickness="1" MinHeight="40" Margin="0,0,0,10" Padding="5">
            <wpfMath:FormulaControl x:Name="ResultDisplay" Formula="" VerticalAlignment="Center" Scale="18" />
        </Border>

        <Grid Grid.Row="2">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>

            <Button Content="rad" Grid.Row="0" Grid.Column="0" Style="{StaticResource FunctionButton}" Click="ModeButton_Click" x:Name="AngleModeButton"/>
            <Button Content="π" Grid.Row="0" Grid.Column="1" Style="{StaticResource FunctionButton}" Click="ConstantButton_Click" Tag="\pi"/>
            <Button Content="e" Grid.Row="0" Grid.Column="2" Style="{StaticResource FunctionButton}" Click="ConstantButton_Click" Tag="e"/>
            <Button Content="C" Grid.Row="0" Grid.Column="3" Style="{StaticResource OperatorButton}" Click="ClearButton_Click"/>
            <Button Content="⌫" Grid.Row="0" Grid.Column="4" Style="{StaticResource OperatorButton}" Click="BackspaceButton_Click"/>

            <Button Content="sin" Grid.Row="1" Grid.Column="0" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\sin"/>
            <Button Content="cos" Grid.Row="1" Grid.Column="1" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\cos"/>
            <Button Content="tan" Grid.Row="1" Grid.Column="2" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\tan"/>
            <Button Content="log" Grid.Row="1" Grid.Column="3" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\log_{10}"/>
            <Button Content="ln" Grid.Row="1" Grid.Column="4" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\ln"/>

            <Button Content="√x" Grid.Row="2" Grid.Column="0" Style="{StaticResource FunctionButton}" Click="FunctionButton_Click" Tag="\sqrt"/>
            <Button Content="x²" Grid.Row="2" Grid.Column="1" Style="{StaticResource FunctionButton}" Click="PowerButton_Click" Tag="^2"/>
            <Button Content="xʸ" Grid.Row="2" Grid.Column="2" Style="{StaticResource FunctionButton}" Click="OperatorButton_Click" Tag="Pow"/>
            <Button Content="(" Grid.Row="2" Grid.Column="3" Click="OperatorButton_Click" Tag="("/>
            <Button Content=")" Grid.Row="2" Grid.Column="4" Click="OperatorButton_Click" Tag=")"/>

            <Button Content="7" Grid.Row="3" Grid.Column="0" Click="NumberButton_Click" Tag="7"/>
            <Button Content="8" Grid.Row="3" Grid.Column="1" Click="NumberButton_Click" Tag="8"/>
            <Button Content="9" Grid.Row="3" Grid.Column="2" Click="NumberButton_Click" Tag="9"/>
            <Button Content="÷" Grid.Row="3" Grid.Column="3" Style="{StaticResource OperatorButton}" Click="OperatorButton_Click" Tag="/"/>
            <Button Content="%" Grid.Row="3" Grid.Column="4" Style="{StaticResource OperatorButton}" Click="OperatorButton_Click" Tag="%"/>

            <Button Content="4" Grid.Row="4" Grid.Column="0" Click="NumberButton_Click" Tag="4"/>
            <Button Content="5" Grid.Row="4" Grid.Column="1" Click="NumberButton_Click" Tag="5"/>
            <Button Content="6" Grid.Row="4" Grid.Column="2" Click="NumberButton_Click" Tag="6"/>
            <Button Content="×" Grid.Row="4" Grid.Column="3" Style="{StaticResource OperatorButton}" Click="OperatorButton_Click" Tag="*"/>
            <Button Content="1" Grid.Row="5" Grid.Column="0" Click="NumberButton_Click" Tag="1"/>
            <Button Content="2" Grid.Row="5" Grid.Column="1" Click="NumberButton_Click" Tag="2"/>
            <Button Content="3" Grid.Row="5" Grid.Column="2" Click="NumberButton_Click" Tag="3"/>
            <Button Content="-" Grid.Row="5" Grid.Column="3" Style="{StaticResource OperatorButton}" Click="OperatorButton_Click" Tag="-"/>

            <Button Content="0" Grid.Row="6" Click="NumberButton_Click" Grid.ColumnSpan="2" Tag="0"/>
            <Button Content="." Grid.Row="6" Grid.Column="2" Click="NumberButton_Click" Tag="."/>
            <Button Content="+" Grid.Row="6" Grid.Column="3" Style="{StaticResource OperatorButton}" Click="OperatorButton_Click" Tag="+"/>

            <Button Content="=" Grid.Row="4" Grid.Column="4" Grid.RowSpan="3" Style="{StaticResource OperatorButton}" Background="Orange" Click="EqualsButton_Click"/>

        </Grid>
    </Grid>
</Window>