Question

cos19°30'cos25°30' - sin 19°30'sin25°30'

Answer 1

$cos19^{\circ }30'cos25^{\circ }30'-sin19^{\circ }30' sin25^{\circ}30'=\\\\=cos(19^{\circ }30'+25^{\circ}30')=cos45^{\circ }=\frac{\sqrt2}{2}$