Recent content by Ledsnyder

Homework Statement THe x and y axes have been rotated about the origin through a 45 degree angle to produce the X and Y axes.. Thus, a given point P (x,y) has coordinates in the first coordinate system and (X,Y) in the new coordinate system The orignal equation is y=10sech(x). What is...

I have the equations.I just don't know how to find the new equation based on the coordinates.

Homework Statement 5x^3+10x^2+20x+15 is rotated through the angle 45 degrees to new xy coordinate system.Whats the equation to the coordinate system? Homework Equations The Attempt at a Solution New X= xcos(theta)+ycos(theta) New Y=-xsin(theta)+ycos(theta)

Is there a software(preferably free) that can fit data into a 4 parameter equation? like the generalised logistic function

calculs something similar to this: http://math.stackexchange.com/questions/107292/rapid-approximation-of-tanhx do you also know of any curve fitting software?

Is there a rational function,not series, that approximates e^x ? for example (x+1)/(x+3)

e^(ax)^y the second one

17.3-(17.3)e^(-92.34940680845194549420x)^y)=17.30181504460159157646-((17.3-(17.3)e^((-0.00118329948908244714x)^y)) anyone know how to solve this or a calculator that can?

Does anyone know of an online calculator that can form an equation of a curve with complex values and lots parameters? An advanced curve fitting calculator Y= C1(1/(1+C2e^C3x) for example

Jorrie,your calculator is awesome.i wish there was similar to calculate complex curves I general that don't neccesarily deal with the universe.

It doesn't show the steps but I got this from Wolfram

The closest logistic model i could calculate was 16.997769517/(1+35.79253791478e^-.6025402362228t) Ok but certainly not satisfying. Where t is in billions of years

I found an equation relating hubbles constant and time!It is highly simplified but helpful! http://www.astronomycafe.net/qadir/q679.html da/at = (2/3)*a0* (1/t0) * (t/t0)^-1/3 then dividing by a = a0 (t/t0)^2/3 you get H(t) = H0*(t0/t)

Does anyone happen to know the value of R at time 0 or something close to time 0?