The surface area of a sphere is [tex]4 \pi r^{2} [/tex].
Hence, the surface area of a hemisphere is half that, [tex]2 \pi r^{2} [/tex].
If the base is also included then the surface area will be [tex]3 \pi r^{2} [/tex].
Given,
Diameter = 26 cm
Therefore, Radius = [tex] \frac{26}{2} [/tex] = 13 cm
Thus,
Area = [tex]3 * \pi * 13^{2} = 3 * \pi * 169 = 507 \pi = [/tex] = 1592.8 [tex] cm^{2} [/tex] [approx.]