Theory:

Construct the circumcentre of the \(ΔABC\) with \(AB =5 cm\), \(∠A = 60°\) and \(∠B = 80°\). Also draw the circumcircle and find the circumradius of the \(ΔABC\).
 
Rough sketch:
 
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Step 1: Draw \(ΔABC\) with the given measurements.

Step 2: Build a perpendicular bisector along both side (\(AC\) and \(BC\)) and let it meet at \(S\), which is the circumcenter.

Step 3: \(S\) as center and \(SA = SB = SC\) as radius, draw the circumcircle to pass through \(A\), \(B\) and \(C\). And the circumradius measured \(= 3.9 cm\).
 
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