Trigonometry Identities - Sum/Difference to Identity (Degrees)

Question

Complete the sum/difference identity for this expression

$$	ext{sin}{(135^{\circ} - 315^{\circ})}$$

Accepted Answer

$$=	ext{sin}{(135^{\circ})}	ext{cos}{(315^{\circ})} - 	ext{cos}{(135^{\circ})}	ext{sin}{(315^{\circ})}$$

Answer

$$=	ext{sin}{(135^{\circ})}	ext{cos}{(315^{\circ})} + 	ext{cos}^2{(135^{\circ})}$$