y={[1-cos(兀-2a)]/[(cota/2)-(tana/2)]}-[cos(兀/4-b)]^2=[1+cos(2a)]/【{[cos(a/2)]^2-[sin(a/2)]^2}/[cos(a/2)sin(a/2)]】-[√2/2(cosb+sinb)]^2=2(cosa)^2/[cosa/(1/2sina)]-1/2(1+sin2b)=sinacosa-1/2sin2b-1/2...