Question

(sin12*cos24*sin36*cos48)(sin42*cos54*sin66*cos78)

Answer 1

$frac{sin12^o*cos24^o*sin36^o*cos48^o}{sin42^o*cos54^o*sin66^o*cos78^o}=frac{sin12^o*cos24^o*sin(90^o-54^o)*cos(90^o-42^o)}{sin42^o*cos54^o*sin(90^o-24^o)*cos(90^o-12^o)}=\ =frac{sin12^o*cos24^o*cos54^o*sin42^o}{sin42^o*cos54^o*cos24^o*sin12^o}=1$