Calculating Distance of an Electron Moving in a Plane Using Derivatives

[courtrigrad]

An electron moves in a plane so that at time t its coordinates are

x = a( e^t + e^-t) and y = b(e^t - e^-t) . How fast is its distance from the origin changing?

My solution:

Let Y be the distance from the origin and the point

Then using distance formula I get

Y = [[a( e^t + e^-t) ^2] + [[b(e^t - e^-t)^2]

Do I just find derivative of this?

 

[vincentchan]

y is not the distance between origin and point, r=sqrt(x^2+y^2), do the derivative of r and you will see the answer

 

[courtrigrad]

isnt that what i have??

 

[vincentchan]

one more things, sinhx=(e^x-e^-x)/2 coshx=(e^x+e^-x)/2, hope tis will make the calculation simpler, IF you have not learned the derivative of these yet, just forget it...

 

[dextercioby]

isnt that what i have??

Nope,u miss the square root...

Daniel.