Step-by-step explanation:
as the graphic shows, we are dealing with a special rhombus : a square.
this is proven by the fact that the angle on one side of the diagonal at the corner is 45°. so, the other side must be 45° too, and so we have 90° angles at the corners.
what is not clear to me is : what is 6 cm long ? a half-diameter, or the whole diameter ?
I assume the half-diameter.
what the graphic is trying to suggest is that we have 4 little right-angled triangles that are also isoceles triangles (their legs are equally long).
every leg is 6 cm long (based on my assumption above).
because they are right-angled, the area of each of these little triangles is leg×leg/2
6×6/2 = 18 cm²
we have 4 triangles, so the total area is
4×18 = 72 cm²
if 6 cm stands for the whole diagonal after all, then the only change is the length of the legs, which would be then 6/2 = 3 cm.
then we would have
3×3/2 = 4.5 cm² for a single triangle
and
4×4.5 = 18 cm² for the whole area.
