confusing title i suspect but didnt know what else to call it.//<![CDATA[ aax_getad_mpb({ "slot_uuid":"f485bc30-20f5-4c34-b261-5f2d6f6142cb" }); //]]>

so i'm considering a spring and mass with the displacment of the mass being x and the stiffness of the spring being k

force on the spring = -k*x =m*a

or rearranged etc

d2x/dt2 + (k/m)*x = 0 ...............................................[1]

then i assume a soln of the form e^(at)

and find a= i*(k/m)^.5 [then let sqrt(k/m)= w)

so i get x= e^(i*w*t)

which using the euler identity gives

x= cos(wt)+i*sin(wt)

great so i managed to show that the thing will move sinusoidly

but what about that i*sin(wt) term

if i ignore it, and let x=cos(wt) this still satisfies [1] above

so am i justified in ignoring it? or does it have some physical significance?

or is it something that just gets "thrown up" as a result of me assuming a soln of the form e^at ?

and more generally

if i find a soln to a diff eqn, and find that by dropping some terms in the soln that it still satifies the eqn am i still justified in doing that?

thanks jim

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Significace of i*sin(wt) in SHM [cos(wt)+i*sin(wt)]

Have something to add?

**Physics Forums - The Fusion of Science and Community**