Draw a quadrilateral whose diagonals have equal lengths of \(8\ cm\) that bisect each other, and intersect at an angle of 30\(^\circ\).
 
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Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:

Thus, the rectangle \(ABCD\) is obtained.
Answer variants:
Mark the midpoint of \(AC\) as \(O\).
Draw a line segment \(AC\) of length \(8\ cm\).
Place the protractor at \(O\). Draw a line through \(O\) making an angle of \(30^\circ\) with \(AC\).
With \(O\) as the centre, mark two points on the newly drawn line, one on each side of \(O\). Label them \(B\) and \(D\).
Using a compass, take a radius of \(4\ cm\) (half of the diagonal).
Join the vertices in the order \(A–B–C–D–A\).