if the side of this isosceles triangle are 12cm and base is 8cm whats the height

a = b = 12 cm      ;  c = 8 cm

Pythagoras:       h² + (c/2)² = a²

                         h² = 144 - 16        =>     h =$${\sqrt{{\mathtt{144}}{\mathtt{\,-\,}}{\mathtt{16}}}}$$

$${\mathtt{h}} = {\sqrt{{\mathtt{144}}{\mathtt{\,-\,}}{\mathtt{16}}}} \Rightarrow {\mathtt{h}} = {\mathtt{11.313\: \!708\: \!498\: \!984\: \!760\: \!4}}$$    cm