1. The problem statement, all variables and given/known data I shall be grateful if someone can help me understand this notation: http://files.engineering.com/getfile.aspx?folder=340bee11-1ba4-49b2-9a31-1a747012d69b&file=1.gif I know that this notation will finally/should finally give me the below six equations http://files.engineering.com/getfile.aspx?folder=bced2393-e971-40fe-ad29-fba6ac509567&file=2.gif But I do not know how to expand the above notation. I have uploaded the imapge file to engineering.com as I couldn't upload it here 2. Relevant equations As stated / described abov 3. The attempt at a solution I know the answer but struggling o expand. Tried with notation/calculus but couldn't arrive at it.