ABCD is a parallelogram with A(-1,3,2) B(2,3,-4) and D(0,1,5) Find its area and the obtuse angle between its diagonals.

Question

anonymous · Answer

What is the value of point

anonymous · Answer

C

anonymous · Answer

im not given C

anonymous · Answer

but one thing that I know for sure is that it is not a parallelogram, it is a 3-D shape

anonymous · Answer

cant we find C?

anonymous · Answer

I am not very sure, I am not very good with geometry.

anonymous · Answer

ok thanks anyways

anonymous · Answer

|dw:1363473089726:dw|
use distance formulae

anonymous · Answer

how do you find the obtuse angles between its diagonals? what does it mean by that?

anonymous · Answer

|dw:1363475160845:dw|
M is where the diagonals intersect.
thats the angle they are asking for.

anonymous · Answer

oh ok thanks! :) so how can I figure the angles out if no angles are given?

anonymous · Answer

use cosine rule.

anonymous · Answer

also, the diagonals bisect eachother

anonymous · Answer

alright thanks :)

anonymous · Answer

to find the area, what do i do after I use the distance formula to find the sides