Graphs of lines and circle.

Graphs of lines and circle.
Hari nih menyempat ulangkaji pasal line graphs and circle graph. Aku pi rujuk site nih…
http://tutorial.math.lamar.edu/AllBrowsers/1314/Lines_Circles_PWF.asp
his explanation was quite interesting yet understandable.

A brief about what I have read for line graph
Sometimes, when we are judging about lines, it is better to know, whether the lines are parallel or perpendicular? But how?

First we must know the slope of both lines (say m1 and m2)which we can calculate those by subtracting two point of y-axis (which you call as rise) and divided with the subtraction of two point from x-axis (which you call as run), which we write as follows;

m1 = y2-y1/x2-x1 = rise/run

ok, how to know whether the lines are parallel or perpendicular? It’s easy , just by calculating such as

1) for parallel , m1 = m2
2) for perpendicular, m1=-1/m2

However, there are also another way to detect whether the lines are perpendicular or parallel by using vector. Hope I got time to explain those in a few days from now.

Ok, cam ne pulak ngan circle graph?
Circle graph? Err… does it has relationship with the above explanation?
Pretty much , there is , a bit, I think so!

What do you know about circle? Well, for sure it shapes are round, but how about the distance from the centre till the boundary? Should be all the same , right?
The distance, d can be calculated as follows,

d = ((x2-x1)^2+(y2-y1)^2)^1/2
(note that ^ means power)

However, since the distance from the centre point till the boundary are equal, thus we can rewrite the distance as;

d = ((x-h)^2+(y-k)^2)^1/2

Assuming that the centre point are (h,k). Just to make life easier, we sometimes need to know four strategic point to draw a circle which are shown as follows;

1) the most right point : (h+r,k)
2) the most top point : (h,k+r)
3) the most left point : (h-r,k)
4) the most bottom point: (h,k-r)

just to add somethings which a just read about ,
composition function means you use a function as a variable into the function, such as, say you have f(z)= z^2 and g(z)=z+2
so composition function of f(z) should be written as f(g(z))=(z+2)^2.