шамин с сдо
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f(x) |
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n |
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x |
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f(x) = f(a) + |
f′(a) |
(x − a) + |
f′′(a) |
(x − a)2 + . . . |
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1! |
2! |
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· · · + |
f(n)(a) |
(x − a)n + o((x − a)n). |
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n! |
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f(x) = Pn(x) + o((x − a)n),
Pn(x) |
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Pn(x) = A0 + A1(x − a) + A2(x − a)2 + · · · + An(x − a)n,
Ai |
x = a |
Pn(a) = A0 = f(a).
Pn′ (x) = A1 + 2A2(x − a) + · · · + nAn(x − a)n−1.
x = a
Pn′ (a) = A1 = f′(a).
Pn′′(a) = 2A2 = f′′(a).
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f(k)(a) |
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Ak = |
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, k = 0, 1, . . . , n. |
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k! |
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f(x)
Rn(x) = f(x) − Pn(x).
Rn(a) = Rn′ (a) = · · · = Rn(n)(a) = 0.
lim Rn(x) .
x→a (x − a)n
0
0
n
lim Rn(x)
x→a (x − a)n
f(x) = f(0) +
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R′ |
(x) |
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Rn(n)(x) |
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= lim |
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lim |
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n! = 0. |
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x→a n(x − a)n−1 |
= · · · = x→a |
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Rn(x) = o((x − a)n).
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a = 0 |
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f′(0) |
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f′′(0) |
2 |
f(n)(0) |
n |
n |
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x + |
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x + · · · + |
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x + o(x ). |
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1! |
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2! |
n! |
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n
Ex
f(x) = ex |
a = 0 |
f(k)(x) = ex, f(k)(0) = 1,
ex = 1 + |
x |
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x2 |
xn |
+ o(xn). |
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+ · · · + |
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1! |
2! |
n! |
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SIN X |
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f(x) = sin x |
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a = 0 |
k |
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f(k)(x) = sin x + k |
π |
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2 |
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f(0) = 0, f(2m)(0) = sin mπ = 0,
f(2m−1)(0) = sin mπ − |
π |
= (−1)m−1, |
m = 1, 2, 3, . . . . |
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2 |
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sin x = x |
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x3 |
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x5 |
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+ ( 1)m−1 |
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x2m−1 |
+ o(x2m). |
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3! |
5! − · · · |
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(2m |
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1)! |
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COS X |
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f(x) = cos x |
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a = 0 |
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k |
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f(k)(x) = cos x + k |
π |
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2 |
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f(0) = 1, f(2m)(0) = (−1)m,
f(2m−1)(0) = 0, m = 1, 2, 3, . . . .
cos x = 1 − |
x2 |
x4 |
m x2m |
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2m+1 |
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− · · · + (−1) |
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+ o(x |
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2! |
4! |
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(2m)! |
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(1 + X)α |
f(x) = (1 + x)α |
α |
a = 0 |
k |
f(k)(x) = α(α − 1) . . . (α − k + 1)(1 + x)α−k ,
f(0) = 1, f(k)(0) = α(α − 1) . . . (α − k + 1).
(1+x)α = 1+αx+ |
α(α − 1) |
x2+ |
· · · |
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α(α − 1) . . . (α − n + 1) |
xn+o(xn). |
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2! |
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n! |
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n = 2 |
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1 |
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= 1 − x + x2 + o(x2), |
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1 + x |
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√ |
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1 + x = 1 + |
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x − |
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x + o(x ), |
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2 |
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= 1 − |
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x + |
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x + o(x ). |
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√ |
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2 |
8 |
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1 + x |
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LN(1 + X)
f(x) = ln(1+x) |
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a = 0 |
k |
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f(k)(x) = |
(−1)k−1(k − 1)! |
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(1 + x)k |
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f(0) = 0, f(k)(0) = (−1)k−1(k − 1)!. |
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f(x) = ln(1 + x) |
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x2 |
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x3 |
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xn |
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ln(1 + x) = x − |
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− · · · + (−1)k−1 |
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+ o(xn). |
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3 |
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n + 1 |
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f(n)(x) |
[a, x] |
[x, a] |
f(n+1)(x) |
(a, x) x, a |
Rn(f, x) = f(n+1)(a + θ(x − a)) (x − a)n+1,
(n + 1)!
0 < θ < 1
n = 0
f(x) = f(a) + f′(a + θ(x − a))(x − a).
n − 1
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n |
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Rn(f, x) |
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Rn(f, x) − Rn(f, a) |
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(x − a)n+1 |
(x − a)n+1 − (a − a)n+1 |
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= |
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Rn−1(f′, ξ) n |
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(f′)(n)(η) |
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f(n+1)(η) |
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(n + 1)n! |
(n + 1)! |
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(n + 1)(ξ − a) |
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a < η < ξ < x
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f(x) = ex |
ex ≈ 1 + |
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x2 |
xn |
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+ · · · + |
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1! |
2! |
n! |
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x = 1 |
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e |
n = 5
e ≈ 1 + 11 + 12 + 16 + 241 + 1201 ≈ 2.7167.
ln 2 |
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ln(1 + x) |
x = 1 |
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n = 10 |
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1 |
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ln 2 ≈ 1 − |
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− |
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− |
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≈ 0.646. |
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ln 2 ≈ 0.693 |
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ln(1 + x) |
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ex |
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sin x |
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x |
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sin 0.1 ≈ 0.1 − |
0.13 |
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≈ 0.0998. |
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6 |
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x
a
cos x
a = 0
4 |
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n = 6 |
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2 |
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0 |
cos x |
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cosx |
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−2 |
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= 4 |
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−4 |
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= 2 |
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−6 |
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−4 |
−3 |
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x |
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lim |
x3 |
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x→0 sin x − x |
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sin x |
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lim |
x3 |
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= lim |
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x3 |
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= lim |
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6. |
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x |
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x 0 |
sin x |
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x − |
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x 0 |
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o(x |
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→ |
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→ |
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6 + o(x ) − x |
→ |
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x3 |
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lim |
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ln cos x |
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x→0 ex − x − 1 |
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cos x ex |
ln x |
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ln cos x |
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ln(1 |
− |
x22 + o(x3)) |
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lim |
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= lim |
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= |
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+ o(x3) − x − 1 |
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x→0 ex − x − 1 x→0 1 + x + x2 |
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x22 |
+ o(x3) |
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lim |
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= x→0 |
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+ o(x3) |
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= −1. |
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2 |
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