what is the area of a circle if the diameter is 52cm

A=(pi*d^2)/4

                             pi~3,14,  d=diameter  r=radius=d/2

A=(pi*r^2)  

$${\frac{\left({\mathtt{\pi}}{\mathtt{\,\times\,}}{{\mathtt{52}}}^{{\mathtt{2}}}\right)}{{\mathtt{4}}}} = {\mathtt{2\,123.716\: \!633\: \!826\: \!700\: \!229\: \!2}}$$  

$${\mathtt{\pi}}{\mathtt{\,\times\,}}{{\mathtt{26}}}^{{\mathtt{2}}} = {\mathtt{2\,123.716\: \!633\: \!826\: \!700\: \!229\: \!2}}$$

Note that, because the diameter is given with units of cm, Headingnorth's result has units of cm²