Update geometry.tex

changed to vector notation for the first and second question
Update geometry.tex

changed for example $\verticalvector{3,2}$ to $\verticalvector{3\2}$
Update geometry.tex

changes of type:
$\verticalvector{3\1}$ to $\verticalvector{3\\1}$
Merge pull request #1 from sunayana/master

Update geometry.tex