Locus (1 Viewer)

[Winston]

Hi guys
ive just started yr 12
and i do ITS and i am on work placement for a week
and i have to learn about locus on my own
witht he notes, but they dont make sense at all..

can anyone guide me to any guides on the net or even help me out on understanding it


im not getting questions like this


e.g.

find the loc if the distnace from the line y=2 equals the distance from the line x=-1


thanks everyone...

 

[spice girl]

As with all other locus questions, these are the crucial steps:

1) You say P(Xp, Yp) satisfies your criteria.

2) You use the criteria to find a relationship between Xp and Yp. Using your example, it's the distance from y=2 equals distance from x=-1
Distance of P from line (y=2) is |Yp - 2|
Distance of P from line (x=-1) is |Xp - (-1)| = |Xp + 1|
Equate the two:
a) Yp - 2 = Xp + 1
=> Yp - Xp - 3 = 0
b) 2 - Yp = Xp + 1
=> Yp + Xp - 1 = 0

3) Change Xp, Yp into x, y; to get your cartesian expression
Locus: y - x - 3 = 0
and y + x - 1 = 0

 

[Winston]

hmm im still a bit confused
im just confused what they are exactly asking u to do..

 

[Jellymonsta]

the locus is the path travelled by a particle under certain conditions.
eg a circle can be described as a particle with locus r units away from o at all times.
a parabola is the locus of a particle equidistant from a point and a line
for the above example, the locus will be parallel and perpendicular to y=x
its a way of describing cartesian equations without using mathematical terms... you have to do this.

 

[spice girl]

Hmm...
Like Jellymonsta says...

A cartesian equation expresses x in relation to y. You can think of a locus as the complete set of solutions (x,y) that satisfy the equation. i.e. the complete set of points that make up the curve that the equation describes.

Often, you'll be given an algebraic or geometric constraint and asked to find the locus of that. Really, what tey are asking you to do is to interpret the algebra or geometry in terms of cartesian equations.

So, they ask you to "Find the locus of point P" where P satisfies some sort of condition, in your case, equidistance to two lines.

What don't u understand now?

 

[Winston]

im sorry i duno wat a cartesian plane or wateva it is
can u try ot interpret sum of ur explanations through a diagram if u dont mind
ill be real happy i tend to understand it more via a diagram or picture
thanks jellymonsta and spice girl

 

[enak]

Sup winnie
Cartesian plane is just an x and y axis from -infinity -> +infinity

eg
edit: ffs, cant draw the graph

see

 

[spice girl]

Originally posted by Winston
im sorry i duno wat a cartesian plane or wateva it is
can u try ot interpret sum of ur explanations through a diagram if u dont mind
ill be real happy i tend to understand it more via a diagram or picture
thanks jellymonsta and spice girl

When you draw graphs, you have an x horizontal axis and a y vertical axis. That is the cartesian plane.

A cartesian equation is just an equation linking x to y
e.g. y = x^2
y = 2x + 3
x^2 + y^2 = 4

 

[Winston]

Hey spice girl
i thank u for all the patience u have had to try to help me understand it
but i really dont understand it
so far i know im fucked and and stupid and hopeless
but yeah i wont asked anymore further
just wanted to say thanks for helping me

 

[spice girl]

no worries

maybe u should find a tutor, at least for a few months to brush up on some basics...

 

[Winston]

Originally posted by spice girl
no worries

maybe u should find a tutor, at least for a few months to brush up on some basics...

Well i dont have that kind of money to find a tutor, but yeah
ahh i guess im just not made for education
i suck...