No.32

The Standard Deviation is a measure of how spread out numbers are.Its symbol is σ (the greek letter sigma). The formula is easy: it is the square root of the Variance. So now you ask, "What is the Variance?". The Variance is defined as the average of the squared differences from the mean. 

Example:

The heights (at the shoulders) are: 600mm, 470mm, 170mm, 430mm and 300mm. Find out the Mean, the Variance, and the Standard Deviation. Your first step is to find the Mean:

Mean =	600 + 470 + 170 + 430 + 300	=	1970	= 394
	5		5

No.31

No.30

The hyperbola is centered on a point (h, k), which is the "center" of the hyperbola. The point on each branch closest to the center is that branch's "vertex". The vertices are some fixed distance a from the center. The line going from one vertex, through the center, and ending at the other vertex is called the "transverse" axis. The "foci" of an hyperbola are "inside" each branch, and each focus is located some fixed distance c from the center.

No.29

An ellipse usually looks like a squashed circle. By placing an ellipse on an x-y graph (with its major axis on the x-axis and minor axis on the y-axis), the equation of the curve is:

x²/a² + y²/b² = 1

(similar to the equation of a hyperbola: x²/a² − y²/b² = 1, except for a "+" instead of a "−")

No.28

A parabola is a curve where any point is at an equal distancefrom:

• a fixed point (the focus), and
• a fixed straight line (the directrix)

• the axis of symmetry (goes through the focus, at right angles to the directrix)
• the vertex (where the parabola makes its sharpest turn) is halfway between the focus and directrix.

No.27

The current pi memory champion is a retired Japanese engineer Akira Haraguchi, who in 2006 recited 100,000 digits in front of witnesses in Tokyo. The event took nearly 17 hours. Previously, Mr. Haraguchi set three earlier records by reciting 54,000 digits in September 2004, 68,000 digits in December 2004, and 83,431 in July 2005. To date, however, the Guinness Book of World Records has not officially verified Haraguchi’s attempts.The current Guinness-record holder for memorized digits of pi is held by Lu Chao, a 24-year-old student from China, who recited 67,890 digits in 24 hours and four minutes.

No.26

Math is the greatest thing that God created. This song is basically about how math is closely related to our daily life.