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## Homework Statement

2. Homework Equations [/B]

Given in the question.

## The Attempt at a Solution

[/B]

For part a I obtained an expression for the the dipole moment:

##P(t)= P_0 cos(wt)##

And therefore, for part b, I obtained the expressions

##\frac{dP}{dt} = -wP_0 sin(wt)## and ##\frac{d^2P}{dt^2} = -w^2P_0 cos(wt)##.

Now when I make use of Eq. 1.39 to obtain ##E_\theta## for part c), I substitute in the above expression for ##\frac{d^2P}{dt^2}##, but end up with the cos term being ##cos(wt)## from ##\frac{d^2P}{dt^2}## as opposed to ##cos(kr-wt)## which is required. Not sure where I'm going wrong.