The Plus Sign In Left Half Circle symbol (⨭). Copy and paste it, or use its Unicode, HTML, and CSS codes.
More from Math.
The quickest way is to copy ⨭ from this page and paste it anywhere. You can also insert it with its Unicode, HTML, or alt code listed above.
⨭ is U+2A2D (decimal 10797).
Use ⨭ in HTML to render ⨭ on a web page.
On Windows you can type it with Alt+10797 (hold Alt and enter the number on the numeric keypad).
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