Valhalla Legends Archive

Could someone help me with loci please. I got exams coming up and dont have a clue what it is or how to work it out. Thanks

Hey I think I was just learning about that, and there was more than one definition depending on which shape you're talking about.

Given a certain attribute, the locus of that attribute is the collection of all the points that satisfy this attribute such that any other point that doesn't belong to this locus doesn't satisfy this attribute.

Classic example: A circle whose center is (a, b) and whose radius is R is defined as the locus of all points with distance R from the point (a, b).

There are many questions and riddles to be asked about loci. Can you give a specific example you couldn't figure out?

I was given a revision sheet but all it said on it was loci. i cant remember ever doing it.

Sec... Time to get math binder.
Ok there is a definition for atleast 4 shapes which I'm learning this year, and today I'm learning the hyperbola so I'm missing atleast one.

Circle
A circle is a set of (locus) of points equidistant from a fixed point called the center.
The distance from the center to any point on the circle is called the radius.

Equation of a circle with center on (0,0) -- x^2 + y^2 = r^2
Equation of a circle with center anywhere else -- (x-h)^2 + (y-k)^2 = r^2 (where h is vertical displacement and k is horizontal displacement)

Ellipse
The ellipse is obtained by starting with a circle and expanding it horizontally, vertically, or both. Points A and B are located at the endpoints of the longer side, and the line segment between them is called the major axis.
The rest is too hard to explain without a diagram, I'll see if I can scan it in tonight.

Parabola
A parabola is a set of loicus of points equidistant from a dixed line called the directrix (coordinate y) and a fixed point called the focus (location (0,c) for vertical, (c,0) for horizontal).
Parabola opens up: x^2 = 4cy
Parabola opens up: x^2 = -4cy
Parabola opens up: y^2 = 4cx
Parabola opens up: y^2 = -4cx
Once again hard without a diagram, I'll try to scan tonight.

Thanks any help is great

The-Rabid-Lord: You have an exam and no source of exercises that consist of the material that will be on the exam?

I am hopping my mum will come back from the shops with a maths book for me otherwise ill just lose 7-10 marks.

Quote from: The-Rabid-Lord on December 10, 2003, 11:38 AM
I am hopping my mum will come back from the shops with a maths book for me otherwise ill just lose 7-10 marks.

7 - 10 = -3, so therefore you'll gain 3 marks.

The dash/minus sign has more use than just subtraction, such as hyphenation, setting a range, or the nose of a smiley face :-).

Quote from: iago on December 10, 2003, 12:28 PM

Quote from: The-Rabid-Lord on December 10, 2003, 11:38 AM
I am hopping my mum will come back from the shops with a maths book for me otherwise ill just lose 7-10 marks.

7 - 10 = -3, so therefore you'll gain 3 marks.

operator overloading!! come on iago, you shoulda known this one :p

I said I would scan it in, I lied. Not enough time/patience.