Question 1064003
You could calculate the length of two adjacent sides and multiply those lengths.
If you are studying matrices and vectors,
you can calculate the area of any parallelogram
(even one with no right angles)
as the magnitude of the cross product of two side-vectors originating at the same vertex.


SIDE LENGTHS:
{{{EF=sqrt((2-(-2))^2+(3-5)^2)=sqrt(4^2+(-2)^2)=sqrt(16+4)=sqrt(20)}}}
{{{EH=sqrt((2-1)^2+(3-1)^2)=sqrt(1^2+2^2)=sqrt(1+4)=sqrt(5)}}}
{{{area[EFGH]=sqrt(20)*sqrt(5)=sqrt(20*5)rsqrt(100)=highlight(10)}}}