i need some notes for locus as i am struggling. anythin with an explanation into how to get a focus, focal length and directrix wud be greatly appreciated. if ur a SPC boy and understnad weatley, feel free to explain what he is on about. lolll
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Locus!!! (2 Viewers)
- Thread starter penguino
- Start date
Chaosenigma
New Member
- Joined
- Feb 3, 2007
- Messages
- 14
- Gender
- Male
- HSC
- 2007
All locus problems can be expressed into X2=4ay. a is the y distance between the vertex and the directrix/focus
e.g.
y=X2-2x+1
in this case y must = 4ay, disregard the -2x+1
y=X2
4ay=X2
Therefore 'a' =1/4
Now find the vertex using -b/2a
x=2/2, x=1
Sub into equ to find y
y=12-2+1, y=0
Vertex= (1,0)
The focus is 'a' units above the vertex
Therefore focus= (1,1/4)
Directrix is 'a' units below the vertex
y=-1/4
Hope it helped
e.g.
y=X2-2x+1
in this case y must = 4ay, disregard the -2x+1
y=X2
4ay=X2
Therefore 'a' =1/4
Now find the vertex using -b/2a
x=2/2, x=1
Sub into equ to find y
y=12-2+1, y=0
Vertex= (1,0)
The focus is 'a' units above the vertex
Therefore focus= (1,1/4)
Directrix is 'a' units below the vertex
y=-1/4
Hope it helped