## Thursday, August 29, 2013

I got a question today about the difference between nominal, ordinal, ratio and interval data.

Nominal applies to data that consist of names, labels or categories.. Ex: Atlantic, Pacific, India, Arctic....... names of oceans
Ordinal applies to data that can be arranged in order.. example: in a class of 320 students, John ranked 25th, Joe ranked 35th, Amy ranked 10th, Julie ranked 4th
Interval applies to data that also can be arrange in order but the differences in order are important, they are not important in ordinal   ex: temperature.. you can order temperatures and observe meaningful difference
Ratio: data is arranged in order and there is a ratio between the values of the data... ex: length of fish in a river.. 18 inch fish is 3 times the length of a 6 inch fish.. 6 inch fish is 3 times the length of a 2 inch fish, etc

## Saturday, August 24, 2013

For those kids that like math and wish to boost their skills while having fun solving puzzles, here's a good site. It covers math from 1st grade through 6th grade as well as algebra.

http://www.mathsisfun.com/puzzles/

The specific category of puzzles are

starter, measuring, logic, shape, number, algebra, assorted math puzzles and quizzes, card, tricky, Einstein, Sam Loyd, symmetry jigsaw, puzzle games

Give them a shot and have fun!

## Tuesday, August 20, 2013

These are good, enjoy!

These were found at http://www.buzzfeed.com/babymantis/20-spectacularly-nerdy-math-jokes-1opu

## Sunday, August 18, 2013

Enjoy some of these math quotes and jokes!

Mathematics is made of 50 percent formulas, 50 percent proofs, and 50 percent imagination.

"A mathematician is a device for turning coffee into theorems" (P. Erdos)
Addendum: American coffee is good for lemmas.

An engineer thinks that his equations are an approximation to reality. A physicist thinks reality is an approximation to his equations. A mathematician doesn't care.

Old mathematicians never die; they just lose some of their functions.

Mathematicians are like Frenchmen: whatever you say to them, they translate it into their own language, and forthwith it means something entirely different. -- Goethe

Mathematics is the art of giving the same name to different things. -- J. H. Poincare

What is a rigorous definition of rigor?

There is no logical foundation of mathematics, and Gödel has proved it!

## Wednesday, August 14, 2013

the equation for a hyperbola is (x-h)^2/a^2 - (y-k)^2/b^2 = 1 if the transverse axis is horizontal and (y-k)^2/a^2 - (x-h)^2/b^2 = 1 if the transverse axis is the vertical axis.

The transverse axis it eht line segment connecting the vertices.  The foci are located c units from the center, where c^2 = a^2 + b^2.  The center, vertices and foci all lie along the transverse axis. The hyperbola opens along the transverse axis as well.

## Friday, August 9, 2013

Tips for graphing an ellipse.

The equation of an ellipse is (x-h)^2/a^2 + (y-k)^2/b^2 = 1 for an ellipse that is elongated along the x-axis.

The longer axis of the ellipse is the major axis and is of length 2a.  The shorter axis of the ellipse is the minor axis and is of length 2b.

Plot the coordinate of the center (h,k) and move "a" units in each direction from the center along the major axis. Move "b" units from the center in each direction along the minor axis.  These 4 points are the vertices. Then draw a smooth curve through the 4 points.

If you want to plot the foci, you need a value for c, which is found by c^2 = a^2 - b^2.  Move c units from the center along the major axis in both directions and plot the point.

## Monday, August 5, 2013

When graphing a parabola from an equation in standard form, use these steps:

1.  plot the vertez
2.  plot the focus
3.  draw the directrix line
4.  find the latus rectum
5.  draw the parabola

For example, graph the parabola with the equation (x - 2)^2 = 12(y + 1)

The form of a parabola that opens up or down is in the form (x - h)^2 = 4p(y -k),  the vertex is (h,k), the focus is p units from the vertex in the direction the parabola opens, the directix is the line p units from the vertex in the opposite direction.  The latus rectum is 4p.  Plot a point 2p from the focus in both directions to determine the width of the parabola.

1.  the vertex is (2, -1)
2.  the focus is 3 units from the vertex.. Since p is positive the parabola opens up and the focus is at (2, 2)
3.  the directrix is the horizontal line y = -1
4.  the latus rectum is 12, so move 6 units to the left and right of the focus and plots those points.. The points are (8,2) and (-4,2)
5. now draw the parabola

## Thursday, August 1, 2013

How are the conic sections formed?  Use paper and tape to create a double-napped cone. Then, using scissors, you can but the cone in 4 different ways.

1.  A cut that is parallel to the base of the cone.  The cross section on the surface of the cone is a circle.

2.  A cute that is parallel to one of the sides of the cone. The cut will be through the other side of the cone and the base. This cross-section is a parabola.

3.  A cut through both sides of the cone that is not parallel to the base. The cross-section is an ellipse.

4.  A cut vertical through both cones.  The cross-section is a hyperbola.