Given: Diagonal of a square =9√2cm Area of a square =144cm2 Formula used: Area of a triangle = 1/2 × base × height Perimeter of a square =4a Area of a square =a2 Here, a = side of a square Calculation: We know that diagonal of a square =a√2 a√2=9√2 ⇒ a = 9 Perimeter of the square = 4 × 9 = 36 cm = base of the triangle Area of the square = 144 cm^2 ⇒a2=144cm2 ⇒ a = 12 cm = height of the triangle Area of the triangle =1/2×36×12 ⇒18×12=216 ∴ Area of the triangle is 216