1 |m+n|^2=m^2+2mn+n^2 =1+4cosA+5-4sinA =6-4sqr(2)sin(A-π/4)当A=7π/4时，|m+n|^2=6+4sqr(2)=(2+sqr(2))^2|m+n|(max)=2+sqr(2)第二题有问题 应该不是cos(2/A+8/π）而是cos(A/2+π/8）请确认下
sqr是根号
