Pre-calculus/trig

If I understand this.....you  are  looking for   " - - "   ????

Looking at the right side

(1/2) [ sin pi/2 - sin pi/6 ]  =

(1/2) [ 1 - 1/2]  =

(1/2) (1/2)  =   1/4

So

" - - "  pi/3 * sin pi/6   = 1/4

" - - " pi/3 * (1/2) = 1/4           multiply both sides by 2

" - - " (pi/3)  =   1/2

The " - - " is    "cos "