[tex]f(x) = sin^2x \Rightarrow f(x) = (sinx)^2 \Rightarrow f'(x) = [(sinx)^2]^{'} \Rightarrow \\ \\ \rightarrow \ $ Derivam dupa formula (u^n)' = n\cdot u^{n-1}\cdot u' \\ \\ \Rightarrow f'(x) = 2\cdot (sinx)^{2-1}\cdot (sinx)' \Rightarrow f'(x)=2\cdot sinx\cdot cosx[/tex]
