# input for parametric equation for vector

jeandavid54 shared this question 11 years ago

hi,

I need to input this parametric equation for a rotating vector

r(t)=r [u.cos(wt)+v.sin(wt)]

r(t) vector function

u, v : unit vectors for X and Y axes

w angular speed

the function Curve[.....,t,] traces me a circle but that's not what I need

How can I proceed ?

thanks

I know the product k*u (scalar times vector) works well but not in this case. 1

hello

do you mean

a slider (angle or number)

r number

A point

vector[A,A+(r;a)]

saludos 1

no I don't want to write a polar coordinate vector

i want to write an equation r(t) where r is the vector vs time in an 2-dimension reference given by u and v , unit vectors.

this must give me a rotating vector in function of time t 1

Hi, using Mathmagic's advice is basically the best you can do in your case. Maybe you want to do slight modifications:

t time (slider)

w angular velocity (number)

r=u*cos(w*t)+v*sin(w*t)

The "t" parameter must come from a slider, you cannot write "r(t)" on LHS of the equation.

Cheers,

Zbynek 1

t as a slider is a good idea to get around it.

but my idea is to to have a function with variable t that I can derivate to obtain the speed and the acceleration vectors.

I see there are derivative functions set in Geogebra I could use but only for classic functions with x but not parametric ones with t.

may be I have to write some program lines with javascript aside to take account of this possibilities.

best regards

jean 1

You can also define the paramtric curve

a=Curve[sin(p),cos(p),p,1,10]

t ... slider

w = Vector[a(t)]

hide a

and then use Derivative[a]. I remember creating a worksheet using Derivative o parametric curve: http://www.geogebra.org/for...

but I'm sure there are better examples around the forum. 1

thanks !

seems good !