delimiters

• How to Automatically Size Parentheses Across Multiple LaTeX Lines
  Put a multiline expression in an aligned block inside one automatic delimiter pair; use fixed-size delimiters if the rows must stay separate.
• How to Make Big Angle Brackets in LaTeX
  Use \langle and \rangle for angle brackets in LaTeX, then choose automatic sizing with \left and \right or controlled sizes with \bigl and \bigr.