Spesh Qs

[TrueTears]

Is it true/false that if you take the average of the three coordinates of a triangle you will get the coordinates of the centre of the circumcircle?
I've heard that it can be used to find the centroid but i'm not sure if that's the same thing.

Is this that Kilbaha question? |z-c| = r shit?

I just made 3 simultaneous equations to find the centroid.

[/0]

true true

Another Q

If you have a length in and you take the log base 10 of it then do the units stay the same or wut?

[kamil9876]

Can you provide an example of the context?

[TrueTears]

I will provide the example, it is in fact this question:
http://vcenotes.com/forum/index.php/topic,9192.msg167561.html#msg167561

[kamil9876]

ok well because the question says "x cm". x=10 for 10cm, not x=10cm otherwise "x cm" would imply "10cm cm".

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Difference between a maths and physics question:

maths:

Displacement of a particle x m from the origin at time t seconds after blah blah is given by:

where

physics:

Displacement of a particle,x , at a time t after blah blah is given by:

where

[/0]

thanks kamil... it was just a general question

[kamil9876]

yeah, in general what i tried to say (without explicitly saying it) is that mathematical functions take unitless numbers as arguments so really there should be some constant with a unit to cancel out the unit of the quantity, or the quantity can just be defined by a real number as 'how many units'(latter being the case in most applied math questions)

[/0]

If a question asks whether the 'path' of one vector function crosses the path of another vector, what does it mean by 'cross'?

For example, if you had the vector (1,1) and the 'path' r(t) = (t,-t), would that 'cross' the (1,1) vector?

[TrueTears]

I'd assume cross is just that the path of both the vector functions will intersect each other. The particles themselves don't have to intersect at the same time but the paths they travel on will intersect.

r(t) = (t,-t) what notation is that?

[Damo17]

If a question asks whether the 'path' of one vector function crosses the path of another vector, what does it mean by 'cross'?

For example, if you had the vector (1,1) and the 'path' r(t) = (t,-t), would that 'cross' the path of the vector?

I believe if it says 'crosses the path' it means that at some point in time, one vector is at a position where the other is (if collision), or has previously been there.

In your example, no they wouldn't cross, at t=1, one vector would be at (1,1) and the other at (1,-1).

[/0]

lazy notation

according to MAV 2008 in that particular example the paths wouldn't cross... so i wonder if the domain for 'crossing' is something like (0,1), not [0, 1]? or something or rather...

I'd assume cross is just that the path of both the vector functions will intersect each other. The particles themselves don't have to intersect at the same time but the paths they travel on will intersect.

r(t) = (t,-t) what notation is that?

[TrueTears]

Wait r(t) = t i -t j?

[/0]

If a question asks whether the 'path' of one vector function crosses the path of another vector, what does it mean by 'cross'?

For example, if you had the vector (1,1) and the 'path' r(t) = (t,-t), would that 'cross' the path of the vector?

I believe if it says 'crosses the path' it means that at some point in time, one vector is at a position where the other is (if collision), or has previously been there.

In your example, no they wouldn't cross, at t=1, one vector would be at (1,1) and the other at (1,-1).

oh so do you think the path has to go THROUGH the point (1,1), not just through the 'vector' pointing there?

Wait r(t) = t i -t j?

yer

[TrueTears]

If a question asks whether the 'path' of one vector function crosses the path of another vector, what does it mean by 'cross'?

For example, if you had the vector (1,1) and the 'path' r(t) = (t,-t), would that 'cross' the path of the vector?

I believe if it says 'crosses the path' it means that at some point in time, one vector is at a position where the other is (if collision), or has previously been there.

In your example, no they wouldn't cross, at t=1, one vector would be at (1,1) and the other at (1,-1).

oh so do you think the path has to go THROUGH the point (1,1), not just through the 'vector' pointing there?

Wait r(t) = t i -t j?

yer

Yes that what it means by crossing doesn't it? The paths literally have to MEET. [But doesn't have to be at same time]

Quote from: TrueTears on Today at 10:23:52 PM
Wait r(t) = t i -t j?

yer

Okay well x = t and y = -t

so y = -x is the cartesian equation. Since there is no restriction on t, then domain and range of the function is R.

Therefore it won't ever intersect with the point (1,1)

[/0]

mmm cool thanks, it just seems weird seeing as in the question they have OA = 500i+450j which is just a 'point', and yet they ask whether the vector function crosses the 'path' of OA. Wouldn't normally call a point a path rite?