Let us consider rhombus ABCD whose diagonals are AC AND BD whose intersection point is O
we know that diagonals of rhombus are perpendicular to each other .
now in ΔABC,BO IS PERPENDICULAR to AC
THEREFORE AREA of ΔABC =
similarly in ΔADC
area of ΔADC=
AREA OF RHOMBUS=area of ΔABC+area of ΔADC