\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\title{\sc Homework 1}
\author{\sc by Me}
\date{\sc January 2017}
\begin{document}
\maketitle
\noindent 1) Show that $\sqrt{2} \in \mathbb{R} $
\vspace{1pc}
We will define two sequences, $A_k$ and $B_k$.
Let $A_k = a_1.a_2a_3a_4\dots a_k$, and ${A_k}^2 > 2$ but decreasing the last digit, $a_k$,
by 1 will result ${A_k}^2 < 2$.
\end{document}
(Font) <10.95> on input line 12. ! Undefined control sequence. l.12
\noindent 1) Show that $\sqrt{2} \in \mathbb {R} $
I get this error when I try to compile this. I still get a PDF output as I want, but it still bothers me why this error is popping up. I tried including the package amsmath, amstext, but it didn't fix the error.
Best Answer
The error message in the format you have shown above is not readable, you should always preserve line endings when showing TeX errors.
The error on your document is
Which as the help text makes clear shows, by the position of the line break in the message that
\mathbb
is the problematic command that has not been defined.TeX itself can only tell you that it is not defined, not how to define it but google for that command should quickly tell you that you need the package
amsfonts
Adding
makes the document error free, but there are rather a lot of issues with the TeX markup.
The "two letter" font commands are not recommended in latex2e (and not defined by default) it is usually better to use the latex commands, in this case
\scshape
however in general you should avoid font commands in the document and especially in structural commands like\title
and\author
as the whole point of those commands is that they just have plain text with the data and the styling depends on the document class. For similar reasons you should avoid\vspace
and\noindent
and explicit numbering such as1)
.