যদি $\sin 18^{\circ}=\frac{1}{4}(\sqrt{5}-1)$ তবে $\cos 36^{\circ}=?$

$\frac{1}{4}(\sqrt{5}-1)$

$\frac{1}{4}(\sqrt{5}+1)$

$\frac{1}{5}(\sqrt{4}-1)$

$\frac{1}{5}(\sqrt{4}+1)$