christoph
the sides of a rhombus are equal. draw a line line from one bigger angle to the opposite base so that the line is perpendicular to the base. this smaller triangle is 1:1:sqrt2. height is 5 and the base is 5sqrt2. area of a rhombus is height * base = 5 * 5sqrt2 = 25sqrt2.
Agree Chris. A rhombus is like a ||gm with area = bs X ht. the base is given as 5 root 2, therefore, from 90-45-45, the opposite is 5, therefore area is 5 root 2 X 5 = 25 root 2.