Four rods are hinged at their ends to form a convex quadrilateral.
Investigate the different shapes that the quadrilateral can take.
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A rhombus PQRS has an angle of 72 degrees. OQ = OR = OS = 1 unit. Find all the angles, show that POR is a straight line and that the side of the rhombus is equal to the Golden Ratio.
A hexagon, with sides alternately a and b units in length, is inscribed in a circle. How big is the radius of the circle?
Given a square $ABCD$ of sides $10$ cm, and using the corners as
centres, construct four quadrants with radius $10$ cm each inside
the square. The four arcs intersect at $P$, $Q$, $R$ and $S$. Find
the area enclosed by $PQRS$.