how can I add çsymbol in "text" on a part?
Greg, as long as all you require is to have it show as text simply use the Alt+128 (Ç) combination and you're good to go. (Alt+241 for your ± symbol)
Getting it to create a feature with that text (Alt+128 Ç) is a trick for a more advanced session though ... You may need to do a little work but it will happen.
(Hint: If you RMB click the text you can "Dissolve Sketch Text" and fix the intersecting geometry issue though you may want to place the symbol in another sketch)
"Alt+248" will give you the degree symbol
Here is the list of all alt + keys
If you don't want to extrude-cut or boss into the part, you can create a decal with the text and apply the decal.
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