Maths help!

Dunks · 22 Jan 2012 at 15:01

Hey guys, currently having a mild bit of confusion, all is explained in the image below!

Having difficulty understanding why 3! changes to 4!. This is taken from the solutions, it also seems to change to '12' which is neither 3! or 4!.

I'm thinking it must just be an epic mistake in the solutions, anyone care to prove me wrong?

Dunks · 22 Jan 2012 at 15:10

Forgot to mention that sin^3 (w t) = 1/4 (3sin(w t) - sin3(w t))

It's something to do with the 1/4 but I still can't see it

Dunks · 22 Jan 2012 at 15:36

Yeah figured it out, I get to this:

(-A^3 / 3!) * (1/4) which gives me (-A^3 / 24) and 24 = 4!.

Now to see why it changes to 12 further down the line

Dunks · 22 Jan 2012 at 15:53

The joys of non-linear dynamics

Dunks · 22 Jan 2012 at 19:05

davedudes said:
I think someone is trying to show off.

Not really, I should be hanging my head in shame

Dunks · 22 Jan 2012 at 22:53

jonas123 said:
been a long time since i did this stuff but isn't theta dot = wAcosw?

Yes, yes it is

, my bad. theta'' is correct luckily though

Danza, 4th year Mechanical Engineering.