Find the area of a parallelogram ABCD in which AB = 60cm, BC = 40cm and AC = 80 cm. [Given: = 3.87]

Let the sides of the triangle ABC be:

a = 40 cm, b = 80 cm and c = 60 cm

∴ s =

=

=

= 90 cm

Now, by using Heron’s formula we get:

Area of

=

=

=

= 30 × 10

= 300 × 3.87

= 1161 cm^{2}

As we know that, the diagonal of a parallelogram divides it into two triangles of equal areas

∴ Area of parallelogram (ABCD) = 2 × Area of ()

= 2 × 1161

= 2322 cm^{2}

30