Vectors question?

the points A, B and C have coordinates (3, -1, 5), (7, 1, 3) and (-5, 9, -1) respectively.





a)If L is the midpoint of AB and M is the midpoint of BC, find the vectors LA, BM and LM (LA, BM and LM have a arrow above them)





b) Find the amgle between LM and AB (LM and AB have a arrow above them)

Vectors question?
a.The midpoint of AB is calculated like this.. you take the x of A and the X of being and add them together, thendivide by two (same for y and z)


So.. L= (5,0,4)


then find the midpoint M ( 7+(-5)=2/2=1, 1+9=10/2=5, 3+(-1)=2/2=1 )


To get the vectors then its the second letter minus first..


LA= (-2,-1,1)


make sense?