Question

Sin(-330)cos(-300)+sin(-420)cos390=-1/2 prove that

Answer 1

sin(-330)= -1/2

cos(-300)= - 1/2

sin (-420)= -√3/2

cos 390= √3/2

sin(-330)cos(-300)+ sin(-420)cos390

= (-1/2)*(-1/2)+(-√3/2)*(√3/2)

= (1/4)+(-3/4)

= (1-3)/4

= -2/4

= -1/2