.
For each parallelogram, its area is the product of the lengths of any two its adjacent sides
by the sine of the angle between them
Area =
.
For a rhombus, this formula takes the form
Area =
,
where "a" is the length of any side and
is any of the four angles of the rhombus.
Thus in our case
40 =
,
=
=
,
and an acute angle of the rhombus is
=
= arcsin(0.17778) = 0.17873 radians = 10.25 degrees (approximately). ANSWER
Solved.
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See the lesson
- Area of a parallelogram
in this site.