$OGH$ is an isosceles right-angled triangle:
 
Lines $AB$, $CD$, $EF$, and $GH$ are parallel.

Suppose the area of the smallest triangle $OAB$ is one square unit.

• If lines $OC$ and $AB$ have the same length, calculate the area of trapezium $ABDC$.
• If lines $OE$ and $CD$ also have the same length, calculate the area of trapezium $CDFE$.
• If lines $OG$ and $EF$ also have the same length, calculate the area of trapezium $EFHG$.

Suppose that the chain of trapezia continued. 

What would be the area of the $n^{th}$ trapezium in the chain?

Can you explain your results?