设0
问题描述:
设0
答
L是长度,则L^2=(COSθ-2-SINθ)^2 + (SINθ-2+COSθ)^2=2(COSθ-2)^2+2(SINθ)^2
= 2(COSθ)^2 +8-8COSθ +2(SINθ)^2=10-8COSθ