sin[(2n-1/2)π-α]+cos[(2n+1/2)π+α],
=sin(-π/2-a)+cos(π/2+a)
=-sin(π/2+a)+cos(π/2+a)
=-sin(π/2-a)-sina
=-cosa-sina
=-√2(sina+π/4)
sin[(2n-1/2)π-α]+cos[(2n+1/2)π+α],
=sin(-π/2-a)+cos(π/2+a)
=-sin(π/2+a)+cos(π/2+a)
=-sin(π/2-a)-sina
=-cosa-sina
=-√2(sina+π/4)