When the diagonals of a quadrilateral are perpendicular, the area of that quadrilateral is half the product of their lengths. .. A = (1/2)*d₁*d₂ Substituting the given information, this becomes .. 58 in² = (1/2)*(14.5 in)*d₂ .. 2*58/14.5 in = d₂ = 8 in
