Area of a square $= \frac{(\ldots \ldots . .)^{2}}{2} .$

Write True or False and justify your answer.
If $a, b, c$ are the lengths of three sides of a triangle, then area of a triangle $= \sqrt{s(s-a)(s-b)(s-c)}$, where $s = \text{perimeter of triangle}$.

Find the area and the perimeter of a regular hexagon having length of each side $12\,cm$.

The perimeter of a triangle is $50 \, cm$. One side of a triangle is $4 \, cm$ longer than the smaller side and the third side is $6 \, cm$ less than twice the smaller side. Find the area of the triangle.

In Heron's formula,$s$ represents ............

Find the area of a triangle,two sides of which are $15\,cm$ and $28\,cm$ and the perimeter is $84\,cm$. (in $,cm^2$)