Find area of rectangle whose length is 3 cm and 1 diagnal is 5 cm

you must find the other side of rectangle using Pythagorean theorem where 5 is the hypotenuse and 3 is one of the legs. you will find out that the other leg is 3 cm. then find the area of the triangle 1/2bh using 4 as the height and 3 as the base.