We assume that we need to find the length of the side of the rhombus.

Let

a = the length of the side of the rhombus, a>0

<a = 40 degrees is any interior angle

A = 500 m^2 is the area of the rhombus

Since the area of the rhombus can be calculated by using the formula:

A = a^2 sin <a 

we plug the values into the last equation:

a^2 sin(40) = 500

........

click here to see the equation solved for a

........

a = 27.89 m

We need to ignore the negative solution -27.89, since the length can only be positive.

The length of the rhombus's side is 27.89 meters.