Suppose A(3,0), B(4,5), C(-1,4), D(-2,-1) are the four consecutive sides of the rhombus such that AC and BD are the diagonals.
Area of rhombus is 12×d1×d2, where d1 and d2 are the lengths of the two diagonals
d1=AC=√{3−(−1)}2+{0−4}2=4√2
d2=BD=√{4−(−2)}2+{5−(−1)}2=6√2
Area=12×d1×d2=12×4√2×6√2=24