square of the length of the radius, or as it is often phrased “pi rsquared.” There are
other ways to consider the value of pi: 2 pi (2π) in radians is 360 degrees; thus, pi radi-
ans is 180 degrees and 1/2 pi (1/2π) radians is 90 degrees. (For more about pi and radi-
ans, see “Geometry and Trigonometry.”)
What is the importance of pi? It was used in calculations to build the huge cathe-
drals of the Renaissance, to find basic Earth measurements, and it has been used to
solve a plethora of other mathematical problems throughout the ages. Even today it is
used in the calculations of items that surround everyone. To give just a few examples,
it is used in geometric problems, such as machining parts for aircraft, spacecraft, and
automobiles; in interpreting sine wave signals for radio, television, radar, telephones,
and other such equipment; in all areas of engineering, including simulations and the
modeling of a building’s structural loads, and even to determine global paths of air-
craft (airlines actually fly on an arc of a circle as they travel above the Earth).What is the value of pi?
Pi is a number, a constant, and to 20 decimal places it is equal to 3.141592653589- But it doesn’t end there: Pi is an infinite decimal. In other words, it has an
infinite number of numbers to the right of the decimal point. Thus, no one will ever
know the “end” number for pi. Not that mathematicians will stop trying any time
soon. Today’s supercomputers continue to work out the value of pi, and to date,
researchers have taken the number to more than two hundred billion places. (For
more about pi and computers, see “Math in Computing.”)
Who first determinedthe value of pi?
People have been fascinated by pi throughout history. It was used by the Babylonians
38 and Egyptians; the Chinese thought it stood for one thousand years. Some even give
What are some special properties of zero?
T
here are many special properties of zero. For instance, you cannot divide by
zero (or have zero as the denominator [bottom number] of a fraction). This is
because, simply put, something cannot be divided by nothing. Thus, if some equa-
tion has a unit (usually a number) divided by zero, the answer is considered to be
“undefined.” But it is possible to have zero in the numerator (top number) of a
fraction; as long as it does not have zero in the denominator (called a legal frac-
tion), it will always be equal to zero. Other special properties of zero include: Zero
is considered an even number; any number ending in zero is considered an even
number; when zero is added to a number, the sum is the original number; and
when zero is subtracted from a number, the difference is the original number.