$\mathrm {A+B=\dfrac{\pi}{4}}$ হলে, $\mathrm {\cos ^{2} A-\cos ^{2} \mathbf{B}}$ এর মান কোনটি?

$\dfrac{1}{\sqrt{2}}~ \cos (\mathrm{A}-\mathrm{B})$

$\dfrac{1}{\sqrt{2}} ~\sin(\mathrm{B}-\mathrm{A})$

$\dfrac{\sqrt{3}}{2} ~\cos (\mathrm{A}-\mathrm{B})$

$\dfrac{\sqrt{3}}{2} ~\sin (\mathrm{B}-\mathrm{A})$