Check the picture below.
so, assuming d1 and d2 are the diagonals of it, bearing in mind that the diagonals of a rhombus bisect each, cut in equal halves, then we can get the area of one of those 4 congruent triangles in the rhombus, notice each triangle has a base of 6 and a height of 10.
![\bf \stackrel{\textit{area of the 4 triangles}}{4\left[ \cfrac{1}{2}(6)(10) \right]}](https://tex.z-dn.net/?f=%5Cbf%20%5Cstackrel%7B%5Ctextit%7Barea%20of%20the%204%20triangles%7D%7D%7B4%5Cleft%5B%20%5Ccfrac%7B1%7D%7B2%7D%286%29%2810%29%20%5Cright%5D%7D)
so, assuming d1 and d2 are the diagonals of it, bearing in mind that the diagonals of a rhombus bisect each, cut in equal halves, then we can get the area of one of those 4 congruent triangles in the rhombus, notice each triangle has a base of 6 and a height of 10.