The vectors 
and 
define the parallelogram 
.
Let 
and 
. At what value of the x does the parallelogram become a rectangle?
On line BC lies point E such that 
. Point F bisects side CD, distances AE and BF intersect at point S. Calculate the ratio 
.
Calculate the length of the vector 
if 
, 
and 
. The angle between the vectors 
and 
measures 
.
we accept.
