$\mathrm{f}\left(\mathrm{x}\right)=cos\mathrm{x}$ হলে-

i. ${\mathrm{f}}^{\text{'}}\left(2\mathrm{t}\right)=-sin2\mathrm{t}$

ii. $\int \mathrm{f}\left(\frac{\mathrm{\pi }}{2}-\mathrm{x}\right)\mathrm{dx}=-cos\mathrm{x}+\mathrm{c}$

iii. ${\int }_0^{\frac{\mathrm{\pi }}{4}}\mathrm{f}\left(2\mathrm{x}\right)\mathrm{dx}=\frac{1}{2}$

নিচের কোনটি সঠিক?