已知两向量op1=（cosθ,sinθ),op2=（1,-1）,则向量p1p2模的最小值是?

P1P2 = OP2-OP1=(1-cosθ,-1-sinθ)
|OP2-OP1|^2
=(1-cosθ)^2+(-1-sinθ)^2
= 3 +2(sinθ-cosθ)
= 3+2√2sin(θ-π/4)
min P1P2 = √(3-2√2)结果不能化简么？怎么化简啊leta - c√d = √(3-2√2) (a - c√d)^2 = (3-2√2)a^2+c^2d - 2ac√d = 3-2√2=> d = 22ac = 2(1)a^2+2c^2 = 3 (2)solving (1) (2)a = -1, c =1√(3-2√2) = √2-1