Step 4 is correct.
To start with - the problem.
The working I've done so far.
Which means that or
I'm just not sure if step 4 is correct. Can I simply ignore one of the options because is invalid?
take everything to the right hand side
now you have to factorise
i would replace the cos with y first
so x=70.53 or 289.47 (2dp)
and i have used x instead of theta