Find the mistake .. :
  
  We said we were discussing certain matter then.


so what about this answer:


  We said we were discussing a certain matter then.


do you think the question is wrong and there's no mistakes in the sentence? and what about the answer?


Question: Calculating coordinates with postscript
Answer: It isn't clear if you want to do the calculation in TeX or PostScript, in PostScript that would be

0.5 45 cos mul 8 add 0.5 45 sin mul 8 add


as you can check by typing to gs (or any other PostScript interpreter):

GS&gt;0.5 45 cos mul 8 add 0.5 45 sin mul 8 add pstack
8.35355377
8.35355377
GS&lt;2&gt;