∫ [-1,1]x(1-2x)^2 √(1-x^2) dx =∫ [-1,1](x+4x^3-4x^2) √(1-x^2) dx =-∫ [-1,1]4x^2√(1-x^2) dx =-2∫ [0,1]4x^2√(1-x^2) dx 然后只有用三角代換了x=cost,dx=-sintdt,x=0,t=π/2,x=1,t=0=-2∫ [π/2,0]4cos^...=∫ [-1,1](x+4x^3-4x^2) √(1-x^2) dx =-∫ [-1,1]4x^2√(1-x^2) dx 這步是怎么轉(zhuǎn)化來(lái)的...被積函數(shù)是奇函數(shù)，積分限關(guān)于原點(diǎn)對(duì)稱(chēng)，積分值等于0