9.74.2 Greatest hits from previous weeks

9.74.2.1 Crop an inserted image?
9.74.2.2 How to write two dot above a letter?
9.74.2.3 How can I get bold math symbols?
9.74.2.4 Commenting out large sections
9.74.2.5 Math symbol question: Vertical bar for ''evaluated at ...''
9.74.2.6 Why do the less than symbol (<) and the greater than symbol (>) appear wrong as upside down exclamation (A^\[DownExclamation]) or question mark (A^\[DownQuestion])?
9.74.2.7 Nice scientific pictures show off
9.74.2.1 Crop an inserted image?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=57418

I'm inserting an image with a simple: 
\includegraphics[height=5cm]{filename.png} 
This results in an image that maintains the aspect ratio, and so gives me something like 6cm width. I only really ... 
[graphics] [crop]
 
asked by naught101 https://tex.stackexchange.com/landing/r/digest?cta=user&id=13192 Score of 317
answered by Tobi https://tex.stackexchange.com/landing/r/digest?cta=user&id=4918 Score of 485
9.74.2.2 How to write two dot above a letter?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=152951

the two dots above a letter represents two derivative of varible t. 
My method: 
\documentclass[UTF8]{ctexart} 
\usepackage{amsmath} 
\usepackage{amssymb} 
\usepackage{graphicx} 
\usepackage{epstopdf} 
\... 
[math-mode] [accents]
 
asked by mma https://tex.stackexchange.com/landing/r/digest?cta=user&id=43727 Score of 143
answered by Cain https://tex.stackexchange.com/landing/r/digest?cta=user&id=28428 Score of 198
9.74.2.3 How can I get bold math symbols?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=595

To make Latin-letter variables bold I can use e.g. \mathbf{a}, but while putting Greek letters or symbols such as \nabla inside \mathbf doesn't cause any errors or warnings, it also doesn't do ... 
[fonts] [math-mode] [symbols] [bold]
 
asked by Michael Underwood https://tex.stackexchange.com/landing/r/digest?cta=user&id=32 Score of 621
answered by Mark Meckes https://tex.stackexchange.com/landing/r/digest?cta=user&id=206 Score of 530
9.74.2.4 Commenting out large sections

https://tex.stackexchange.com/landing/r/digest?cta=question&id=17816

To "comment out" a line, I need to insert a % at the beginning of the line (so that the line will not be compiled). 
Is there a way to comment out a large section without having to manually ... 
[comments]
 
asked by user5419 https://tex.stackexchange.com/landing/r/digest?cta=user&id=5419 Score of 441
answered by Martin Scharrer https://tex.stackexchange.com/landing/r/digest?cta=user&id=2975 Score of 352
9.74.2.5 Math symbol question: Vertical bar for ''evaluated at ...''

https://tex.stackexchange.com/landing/r/digest?cta=question&id=40160

How do I insert the line "|" after the equation in LaTeX (see image below)? 
I'm using LyX so if you can point me to the symbol of that line is also OK. 
I don't know if this line has a proper name so ... 
[math-mode] [symbols] [lyx]
 
asked by cidadao https://tex.stackexchange.com/landing/r/digest?cta=user&id=10511 Score of 193
9.74.2.6 Why do the less than symbol (<) and the greater than symbol (>) appear wrong as upside down exclamation (A^\[DownExclamation]) or question mark (A^\[DownQuestion])?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=2369

When typing < or > in LaTeX and compiling with pdflatex, the less than and greater than symbols appear at upside down exclamation points. I'm not in math mode. 
[symbols] [punctuation] [font-encodings]
 
asked by biased_estimator https://tex.stackexchange.com/landing/r/digest?cta=user&id=996 Score of 318
answered by Stefan Kottwitz https://tex.stackexchange.com/landing/r/digest?cta=user&id=213 Score of 287
9.74.2.7 Nice scientific pictures show off

https://tex.stackexchange.com/landing/r/digest?cta=question&id=158668

Task 
Show off your best scientific illustration ! 
The main purpose of this question is to share beautiful scientific pictures, preferably with an educational aspect. 
Content 
Your post must ... 
[diagrams] [3d] [technical-drawing] [fun] [big-list]
 
asked by Thomas https://tex.stackexchange.com/landing/r/digest?cta=user&id=42660 Score of 568
answered by Charles Staats https://tex.stackexchange.com/landing/r/digest?cta=user&id=484 Score of 339