Casio fx-CG10 Advanced Operation Manual page 34

Fostering Advanced Algebraic Thinking with Casio Technology
Investigation 1.4—Douglas Fir Trees
Did You Know?
The modern Christmas tree originated in western Germany. The Germans set up an
adorned fir tree in their homes on December 24, the religious feast day of Adam and Eve.
In the same room, Germans also displayed a Christmas pyramid, a triangular construction
of wood lined with shelves and decorated with evergreens, candles, and a star to hold
th
Christmas figurines. By the 16 century, the traditions of the fir tree, adorned to represent
the Garden of Eden, and the Christmas pyramid had merged and become the Christmas
tree.
Reference: http://www.britannica.com/EBchecked/topic/115737/Christmas-tree
Douglas fir trees are coniferous evergreen trees native to western North America
and eastern Asia. In North America, the Douglas fir trees may grow to heights of
approximately 300 feet with circumferences in excess of 40 feet. Yet, many stands
of Douglas firs are comprised of trees that are much shorter, since many of the
older specimens have already been logged. Douglas firs are some of the best
timber trees in North America, and they are often used for Christmas trees too. The
table shows the height and circumference of a small stand of Douglas firs.