Yes, thank you for letting me know. I had issues with a previous thread where I did not give enough information (where I thought I had).
Also, since you mention it, I do have a lot of difficulty with identities. I just went back through my notes and realized that I had derived this formula...
It appears that I needed to use
$$
\begin{array}{l}
\cos ^{2}(\theta)=\frac{1+\cos (2 \theta)}{2} \\
\sin ^{2}(\theta)=\frac{1-\cos (2 \theta)}{2}
\end{array}
$$
To get the values of cos and sin in the solution. I was not familiar with this formula :nb).
Thank you for your replies. It seems that in trying to post only the relevant parts of the question, I am missing possibly essential information (that I am not picking up myself).
The question in its entirety is:
Reduce to standard form and graph the curve whose equation is ##x^{2}+4 x y+4...
Oh right, I wasn't even thinking about infinity, I was just thinking of it as "undefined"
Also, is this also correct?
##\begin{array}{l}
\cot 2 \theta=0 \\
\frac{\cos 2 \theta}{\sin 2 \theta}=0 \\
\cos 2 \theta=0 \\
2 \theta=90
\end{array}##