Quick response to https://ironscripter.us/powershell-back-to-school-scripting-challenge

BackToSchool.psd1

@{
    ModuleVersion     = "1.0.0"
    RequiredModules   = @()
    FunctionsToExport = @(
      "Get-RightAngledTriangleSides"
      "Get-CircleArea"
      "Get-SphereVolume"
      "Get-CylinderVolume"
      "Get-Factorial"
    )
    RootModule        = "BackToSchool.psm1"
    GUID              = "2809e250-f5cf-42b2-874b-2de2a24d6c33"
    Description       = "Quick attempt at the IronScripter Back to School question"
    Author            = "@jpruskin"
    PowerShellVersion = "5.0"
}

BackToSchool.psm1

function Get-RightAngledTriangleSides {
    <#
        .Synopsis
            Calculates the length of a missing side of a right-angled triangle

        .Example
            Get-RightAngledTriangleSides -A 3 -C 5
    #>
    param(
        # The length of side A
        $A,

        # The length of side B
        $B,

        # The length of side C
        $C
    )
    end {
        switch ($PSBoundParameters.Count) {
            2 {
                [string[]]$ProvidedSides = $PSBoundParameters.Keys
                switch ($Calculating = @("A","B","C").Where{$_ -notin $ProvidedSides}) {
                    "C" {
                        # C^2 = A^2 + B^2
                        $C = [Math]::Sqrt(
                            [Math]::Pow((Get-Variable -Name $ProvidedSides[0] -ValueOnly), 2) + [Math]::Pow((Get-Variable -Name $ProvidedSides[1] -ValueOnly), 2)
                        )
                    }
                    default {
                        # X^2 = sqrt(C^2 - Y^2)
                        $Answer = [Math]::Sqrt(
                            [Math]::Pow($C,2) - [Math]::Pow((Get-Variable -Name $ProvidedSides.Where{$_ -ne "C"} -ValueOnly),2)
                        )
                        Set-Variable -Name $Calculating -Value $Answer
                    }
                }
                continue
            }
            3 {
                if (([Math]::Pow($A,2) + [Math]::Pow($B,2)) -ne [Math]::Pow($C,2)) {
                    Write-Error "Provided Sides Are Not a Valid Right-Angled Triangle"
                }
                continue
            }
            default {
                Write-Error "Please provide two sides of the triangle" -ErrorAction Stop
            }
        }

        [PSCustomObject]@{
            A = $A
            B = $B
            C = $C
        }
    }
}

function Get-CircleArea {
    <#
        .Synopsis
            Gets the area of a circle of given radius / diameter

        .Example
            Get-CircleArea -Radius 3

        .Example
            Get-CircleArea -Diameter 9
    #>
    [CmdletBinding()]
    param(
        # Radius of the circle
        [Parameter(Mandatory, ParameterSetName = "Radius")]
        $Radius = $($Diameter/2),

        # Diameter of the circle
        [Parameter(Mandatory, ParameterSetName = "Diameter", ValueFromPipeline)]
        $Diameter
    )
    process {
        Write-Verbose "The area of a circle is 'π r^2'"
        Write-Verbose "Where:"
        Write-Verbose "  π = $([Math]::Pi)"
        switch ($PSCmdlet.ParameterSetName) {
            "Diameter" {Write-Verbose "  r = ($Diameter / 2)"}
            "Radius"   {Write-Verbose "  r = $Radius"}
        }
        Write-Verbose "r^2 = $([Math]::Pow($Radius, 2))"
        [Math]::Pi * [Math]::Pow($Radius, 2)
    }
}

function Get-SphereVolume {
    <#
        .Synopsis
            Calculates the volume of a sphere, given the radius

        .Example
            Get-SphereVolume -Radius 3
    #>
    [CmdletBinding()]
    param(
        # Radius of the sphere
        [Parameter(Mandatory, ValueFromPipeline)]
        $Radius
    )
    process {
        Write-Verbose "The volume of a sphere is '4/3 π r^3'"
        Write-Verbose "Where:"
        Write-Verbose "  π = $([Math]::Pi)"
        Write-Verbose "  r = $($Radius)"
        Write-Verbose "r^3 = $([Math]::Pow($Radius, 3))"
        4/3 * [Math]::Pi * [Math]::Pow($Radius,3)
    }
}

function Get-CylinderVolume {
    <#
        .Synopsis
            Calculates the volume of a cylinder, given the radius and height

        .Example
            Get-CylinderVolume -R 3 -H 5
    #>
    [CmdletBinding()]
    param(
        # Radius of the cylinder
        [Parameter(Mandatory)]
        $Radius,

        # Height of the cylinder
        [Parameter(Mandatory)]
        $Height
    )
    process {
        Write-Verbose "The volume of a cylinder is 'π r^2 h', or the area of the circular face multiplied by the height"
        $CircleArea = Get-CircleArea -Radius $Radius
        Write-Verbose "  h = $($Height)"
        $Height * $CircleArea
    }
}

function Get-Factorial {
    <#
        .Synopsis
            Calculates the factorial value for a value of N
    #>
    param(
        # Value to calculate for
        [Parameter(Mandatory, ValueFromPipeline)]
        [uint16]$N
    )
    process {
        $Total = 1
        while ($N -gt 0) {
            $Total *= $N--
        }
        $Total
    }
}