Mathematics
Answer
Steps of construction :
Draw a line segment AP.
Draw PX ⊥ AP.
From PX, cut PZ = 3.5 cm.
Through Z, draw EF || AP.
With A as center and radius equal to 6 cm draw an arc cutting EF at C.
Draw QR, perpendicular bisector of AC meeting AP at B.
Join BC.
With A and C as center and radius equal to BC in both cases draw arcs cutting each other at D.
Join AD and CD.

Hence, ABCD is the required rhombus.
Construct a square ABCD, when :