## Trigonometry (10th Edition)

$\sin$ 45$^{\circ}$ = $\cos$ 45$^{\circ}$
According to the Cofunction Identities $\sin$ $A$ = $\cos$ (90$^{\circ}$ - $A$) Therefore: $\sin$ 90$^{\circ}$ = $\cos$ (90$^{\circ}$ - 45$^{\circ}$) = $\cos$ 45$^{\circ}$ Therefore: $\sin$ 45$^{\circ}$ = $\cos$ 45$^{\circ}$