高中数学常用放缩公式之欧阳美创编

i111dx2iix①

i1i；

时间：2021.01.01 i创作：欧阳美 1n1dxii1ln1lni111xnn； nin②

sinisini1③④

1sini12sini11x2sini1dxii1；

(akak1)a2k1akak1x2dx133akak13.

144112222n4n4n12n12n1 (1)

(

121112(n1)n(n1)n(n1)n(n1) CCn1n2)

rTr1Cn(3)

1n!11111(r2)rrr!(nr)!nr!r(r1)r1rn

1n1115(1)11n2132n(n1)2

(4)

111nnnn (5)2(21)2121n2n (6)n2

2(nn1)

(7)

2(n1n)1n11112nn1n2n12n32(2n1)2(2n3)2(8)

欧阳美创编 2021.01.01 欧阳美创编 2021.01.01

欧阳美创编 2021.01.01 欧阳美创编 2021.01.01

11111111,(9)k(n1k)n1kkn1n(n1k)k1nn1k

n11(n1)!n!(n1)!

(10)

1n2(2n12n1)222n12n1n211n22

(11)(11)

2n2n2n2n111(n2)(2n1)2(2n1)(2n1)(2n1)(2n2)(2n1)(2n11)2n112n1

(12)

1n31nnn121111n(n1)(n1)n(n1)n(n1)n1n1

nnnn(13)

22n12n22(31)233(21)221n3213n

k211(14) k!(k1)!(k2)!(k1)!(k2)!

(15)

1nn1(n2)n(n1)i21j21i2j2ij(ij)(i21时间：2021.01.01

(15)

j1)2iji12j121

创作：欧阳美 欧阳美创编 2021.01.01 欧阳美创编 2021.01.01