Explanation

(c)
$\frac{\sin{85{^\circ} - \sin{35{^\circ}}}}{\cos{65{^\circ}}} = \frac{2\cos\frac{85{^\circ} + 35{^\circ}}{5}\sin\frac{85{^\circ} - 35{^\circ}}{2}}{\cos{(90{^\circ} - 25{^\circ})}}$
$\frac{2\cos{60{^\circ}\sin{25{^\circ}}}}{\cos{(90{^\circ} - 25{^\circ})}} = \frac{2.\frac{1}{2}.\sin{25{^\circ}}\ }{\sin{25{^\circ}}} = 1$