Graph the potential of an anharmonic oscillator

[curto]

Homework Statement

my spreadsheet: (oh and please ignore the fact that I've got my amplitude set to 39, i was still answering question 1 when i took the screen shot)

the question i am currently having problems with is question 2:

Homework Equations

i know the potential is U(x) = 1/2kx² but that's about all i know

The Attempt at a Solution

i would use the above equation to find U which would be plotted on the y axis, however i don't know what the constant "k" is. also i don't know what i would use as the x axis

 

[curto]

i figured it out but just for anyone else who would like to know, its actually quite simple. the potential U(x) is equal to the integral of -F dx. simply find an expression for F (remember F = ma = m d^2x/dt^2) and then integrate. that's going to be your expression for U(x). then all you got to do is plot U(x) where x can have any range.