Page 7 - Jose Garcia_2013150017_grade12 ebook

2
BAB PARABOLA

II. Definition and General equation of parabola

look at the picture beside!
point K to point F and to point g have the same distance. If the set or points

are equidistant in a line and a fixed point, then a parabola is obtained. The
fixed line is called the directrix and the point which is not fixed is called

the focal point.

then look at the parabola below!

it is known = ( , 0) is the focus , while the line g is the directrix
suppose the point ( , ) lies on the line then by definition distance PF = distance
0
0
PA.

√( − ) + ( − ) =
2
2

√( − ) + ( − 0)
2
2

0

√( − ) + ( − )
2
2

0
√( + ) + ( − )
2
2
0
0
0

both sides squared are obtained;
2
2
2
( − ) + 0 2 = ( + ) + 0
0
0
2
2
0 2 − 2 + + 0 2 = 0 2 + 2 +
0
0
2
0 2 = 4 run is obtained = 4
0

Note that p is a parameter or distance from peak to focus. Line x = p
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