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u(0) = 0 2 = c<br />

k (ek − 1) + 1 c = k/(ek − 1) <br />

k ∈ N uk(x) = ekx +1<br />

ek + x <br />

−1<br />

k → ∞ 0 ≤ x < 1 u∞(x) = x |u ′ (x)| = 1 <br />

u(0) = 0 uk(1) = 2 k u∞(1) = 2 <br />

[0, 1]<br />

<br />

y ′′ + y = tan x<br />

y ′′ + y = 1<br />

sin x <br />

y ′′ + 3y ′ + 2y = √ 1 + e x<br />

y ′′′ − 3y ′′ + 3y ′ − y = ex<br />

x <br />

<br />

φ(x, c1, c2) = c1 cos x + c2 sin x <br />

<br />

<br />

y(x) = c1(x) cos x + c2(x) sin x.<br />

y ′ (x) = c ′ 1(x) cos x + c ′ 2(x) sin x − c1(x) sin x + c2(x) cos x.<br />

c ′ 1 (x) cos x + c′ 2 (x) sin x = 0 <br />

<br />

y ′ (x) = −c1(x) sin x + c2(x) cos x,<br />

y ′′ (x) = −c ′ 1(x) sin x + c ′ 2(x) cos x − c1(x) cos x − c2(x) sin x.<br />

<br />

−c ′ 1(x) sin x + c ′ 2(x) cos x − c1(x) cos x − c2(x) sin x + c1(x) cos x + c2(x) sin x = tan x.<br />

−c ′ 1 (x) sin x + c′ 2 (x) cos x = tan x <br />

c ′ 1 c ′ 2<br />

<br />

c ′ 1 (x) cos x + c′ 2 (x) sin x = 0,<br />

−c ′ 1 (x) sin x + c′ <br />

cos x sin x<br />

⇐⇒<br />

2 (x) cos x = tan x, − sin x cos x<br />

c ′ 1 (x)<br />

c ′ 2 (x)<br />

<br />

=<br />

0<br />

tan(x)<br />

c ′ 1 (x) = − sin x tan x c′ 2 (x) = sin x c2(x) = − cos x<br />

c1(x) cos x t = tan(x/2)<br />

2 <br />

sin x 1 − cos2 <br />

x<br />

1<br />

c1(x) = − dx = −<br />

dx = sin x −<br />

cos x cos x<br />

cos x<br />

<br />

<br />

<br />

2dt<br />

1 1<br />

<br />

= sin x − = sin x + + dt = sin x + log <br />

1 + t<br />

<br />

1 − t2 1 − t 1 + t<br />

1<br />

− t<br />

<br />

<br />

<br />

= sin x − log <br />

cos(x/2) + sin(x/2) <br />

<br />

cos(x/2)<br />

− sin(x/2) <br />

<br />

<br />

<br />

<br />

¯y(x) = cos x sin x − log <br />

cos(x/2) + sin(x/2) <br />

<br />

cos(x/2)<br />

− sin(x/2) cos x − cos x sin x.<br />

<br />

<br />

<br />

<br />

y(x) = c1 cos x + c2 sin x − log <br />

cos(x/2) + sin(x/2) <br />

<br />

cos(x/2)<br />

− sin(x/2) cos(x).<br />

t = tan(x/2) cos x = 1−t 2<br />

1+t 2 sin x = 2t<br />

1+t 2 dx = 2dt<br />

1+t 2

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