This is my attempt
First I used sum/difference formulae
=-sin(180)cos(x) - - cos(180)sin(x)
=0.cos(x) + (-1)]sin(x)
My another option was to multiply by (-1)
After multiply I have sin (180+x) which I knw Sin(x) is negative in third quadrant(not sure about this method though)
According to my textbook answer is Sin (x)
Where did I lost it??