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Archive for July 2016

Click to download the slide: MO_Practice21.ppsx

I personally think these are something fundamental one must master before they move on to Algebra.

Solar Terms is a calendar of twenty-four periods and climate to govern agricultural arrangements in ancient China and functions even now.

24气节 24气节2

Here is the English version I found from the web:

24气节5

24气节4

Still confused about Solstices, Equinox, Aphelion, Perihelion?

Hope this picture helps:

SolarOrbit

equinox

solstice

aphelion perihelion

Look at the picture, as you can see,
1.  the Sun is not in the middle of the Earth’s orbit.
2. the seasons 四季 on Earth is not caused by the distance from Sun, it’s caused by the “TILT” 倾斜 of Earth’s axis.
3. When the Earth is at “aphelion” (furthest to the Sun) it’s Summer in Northern hemisphere 北半球
4. When the Earth is at “perihelion” (closest to the Sun) it’s Winter in Northern hemisphere

 

In questions involve 3 groups (3 circles in the diagram), it sometimes takes time to understand why

Total = A+B+C – A∩B – B∩C – A∩C + A∩B∩C

Putting up this slides in hope it helps in visualize how we reach the above.

This video is a bit too quiet, but very informative.

We come across this term “albedo” and I find the picture explains it very well:

albedo

Here is the definition:

albedo2

This is a brief and clear video explaining Centroid theorem and how to use it.

“How many triangles with integral side lengths are possible, provided their perimeter is 3636 units?”

To solve the above problem, we can use the Alcuin’s sequence:

alcuinSeq

Now, let’s try another question:

How many possible triangles are there with perimeter of 12 and sides of integral length?

 

** integral length – the length is integer


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