Answer:
[tex]\sqrt{143}[/tex]
Step-by-step explanation:
Use pythagorean theorem to find the missing side.
[tex]a^2+b^2=c^2[/tex]
[tex]1^2+b^2=12^2\\1+b^2=144\\b^2=143\\b=\sqrt{143}[/tex]
This can not be simplified any further.
The third side in simpliest radical form is [tex]\sqrt{143}[/tex].
