Determining the Filter Coefficients of an FIR Filter I need to find the filter coefficients of an FIR filter that will block sinusoids of frequency $200\ \rm Hz$ if the sinusoid is sampled at $1.2\ \rm kHz$. 

I feel like this is a fairly simple problem, but I'm not exactly sure how to go about it.  

I am thinking I need to convert the frequencies to rad/s, then use these values in the transfer function, but am not sure how to find this transfer function.



EDIT: 

I have to choose from one of the possible options: 

$$ \{1, 1, 1\} $$
$$ \{1, -1, 1\} $$
$$ \{1, 0, 1\} $$
$$ \{1, \sqrt{2}, 1\} $$

or None of the Above. 

From the coefficients above, I know the following equations can be created:

\begin{align}
H\left(e^{j\omega}\right)&amp;=1+e^{-j\omega}+e^{-2j\omega}\\
H\left(e^{j\omega}\right)&amp;=1-e^{-j\omega}+e^{-2j\omega}\\
H\left(e^{j\omega}\right)&amp;=1+e^{-2j\omega}\\
H\left(e^{j\omega}\right)&amp;=1+\sqrt{2}e^{-j\omega}+e^{-2j\omega}
\end{align}
The general formula for the frequency response of a causal second-order FIR filter with a pair of complex zeros on the unit circle is

$$H(e^{j\omega})=G(1-e^{j\omega_0}z^{-1})(1-e^{-j\omega_0}z^{-1})\tag{1}$$

where $\omega_0$ is the (normalized) frequency in radians where the zero occurs, and $G$ is a (real-valued) gain constant. If we choose $G=1$ and expand $(1)$ we obtain

$$H(e^{j\omega})=1-(e^{j\omega_0}+e^{-j\omega_0})z^{-1}+z^{-2}=1-2\cos(\omega_0)z^{-1}+z^{-2}\tag{2}$$

In your example we have

$$\omega_0=2\pi\frac{f_0}{f_s}=2\pi\frac{200}{1200}=\frac{\pi}{3}\tag{3}$$

where $f_0$ is the frequency of the zero, and $f_s$ is the sampling frequency. Plugging $(3)$ into $(2)$ with $\cos(\pi/3)=\frac12$ gives

$$H(e^{j\omega})=1-z^{-1}+z^{-2}\tag{4}$$

which corresponds to the impulse response $\{1,-1,1\}$.