# Using Pluto


```{julia}
#| echo: false

import Logging
Logging.disable_logging(Logging.Info) # or e.g. Logging.Info
Logging.disable_logging(Logging.Warn)

import SymPy
function Base.show(io::IO, ::MIME"text/html", x::T) where {T <: SymPy.SymbolicObject}
    println(io, "<span class=\"math-left-align\" style=\"padding-left: 4px; width:0; float:left;\"> ")
    println(io, "\\[")
    println(io, sympy.latex(x))
    println(io, "\\]")
    println(io, "</span>")
end

# hack to work around issue
import Markdown
import CalculusWithJulia
function CalculusWithJulia.WeaveSupport.ImageFile(d::Symbol, f::AbstractString, caption; kwargs...)
    nm = joinpath("..", string(d), f)
    u = "![$caption]($nm)"
    Markdown.parse(u)
end

nothing
```

:::{.callout-note}
## Note
We see in this notebook the use of `let` blocks, which is not typical with `Pluto`. As `Pluto` is reactive – meaning changes in a variable propagate automatically to variables which reference the changed one – a variable can only be used *once* per notebook at the top level. The `let` block, like a function body, introduces a separate scope for the binding so `Pluto` doesn't incorporate the binding in its reactive model. This is necessary as we have more than one function named `f`. This is unlike `begin` blocks, which are quite typical in `Pluto`. The `begin` blocks allow one or more commands to occur in a cell, as the design of `Pluto` is one object per cell.

:::