约å®ï¼â«[a,b]表示[a,b]ä¸çå®ç§¯å
åé¢æ¯:å©ç¨å¥å¶æ§æ±â«[-Ï/2,Ï/2](sinx)^2ln(x+â(4+x^2))dx
解ï¼â«[-Ï/2,Ï/2](sinx)^2ln(x+â(4+x^2))dx (设x=2sht,åæ²å½æ°)
=â«[-acsh(Ï/4),acsh(Ï/4)](sin(2sht))^2.ln((2sht)+â(4+(2sht)^2))d(2sht)
=2â«[-acsh(Ï/4),acsh(Ï/4)](sin(2sht))^2.t.cht dt
å
¶ä¸ u=(sin(2sht))^2æ¯å¶å½æ°,v=t.cht æ¯å¥å½æ°
å¾g(t)=(sin(2sht))^2.t.cht æ¯å¥å½æ°ã
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æ以 â«[-Ï/2,Ï/2](sinx)^2ln(x+â(4+x^2))dx
=2â«[-acsh(Ï/4),acsh(Ï/4)](sin(2sht))^2.t.cht dt
=0
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