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ä¾ä¸ãæ±æ线x=a(t-sint)ï¼y=a(1-cost)çä¸æ±ä¹é¿ã
解ï¼ds=â[(dx/dt)²+(dy/dt)²]dt=aâ[(1-cost)²+sin²t]dt=aâ[2(1-cost)]dt=2asin(t/2)dt
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S=[0ï¼2Ï]2aâ«sin(t/2)dt=[0ï¼2Ï]4aâ«sin(t/2)d(t/2)=-4a[cos(t/2)]︱[0ï¼2Ï]=-4a(-1-1)=8a
ä¾äºãæ±èªæ¬é¾çº¿y=(a/2)[e^(x/a)+e^(-x/a)]=ach(x/a) (a>0)ç顶ç¹Aå°å¦ä¸ç¹Mï¼x ï¼y)ç弧é¿
AâMã
解ï¼yâ²=sh(x/a)ï¼1+yâ²²=1+sh²(x/a)=ch²(x/a)ï¼
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AâM=[0ï¼X]â«â(1+Yâ²²)dx=[0ï¼x]â«ch(x/a)dx=ash(x/a).
注ï¼åæ²æ£å¼¦å½æ°shx=[e^x-e^(-x)]/2ï¼åæ²ä½å¼¦å½æ°chx=[e^x+e^(-x)]/2.
(shx)â²=chxï¼(chx)â²=shx.