# Letter formatting in Latex main and input files

I have created a single file ('main.tex') for letter where I will add other tex files ('letter_1.tex') using \input in Latex. The document format is letter (for cover letters). I am struggling with using the \begin{letter} and \opening commands in the ('letter_1.tex') file as the compiler gives error. If I ignore these commands the compiler runs fine however the formatting is not that good. Please guide on how can I add these two commands and also flush the date to the right side as is normally written in letters.

The codes for the main.tex file is as following;

\documentclass[12pt]{letter}

\usepackage{graphicx}

\usepackage{amssymb,amsmath}
\usepackage{graphicx}
\usepackage{hyperref}

% Entering the following five lines of the codes in main.tex and in letter_1.tex''' results in different margins output (I checked by entering in one file at a time before compiling)
\oddsidemargin=.2in
\evensidemargin=.2in
\textwidth=5.9in
\topmargin=-.5in
\textheight=9in

\begin{document}

\input{letter_1}

\end{document}


The code for the letter_1.tex file is as following;

\today
% \begin{document}
% \begin{letter} {

Person ABC,\\
DEF Faculty,\\
GHI University,\\
Street 1, USA

% }

% \opening{
Dear ABC,
% }

My letter text goes here.

\closing{Yours Truly,

XYZ
}


I am not an expert on the letter class, but a \begin{***} needs and \end{***}, so your letter_1.tex should read:

\begin{letter} {%
Person ABC,\\
DEF Faculty,\\
GHI University,\\
Street 1, USA%
}

\opening{Dear ABC,}

My letter text goes here.

\closing{Yours Truly,

XYZ}

\end{letter}
`

This produces: