.
y = f (x) 0. 0 D D f (x 0)= f (x 0+D ) f (x 0).
y = f (x) 0 D f (x 0) D , D . .
, : = .
=¥, , f 0 .
f 0 :
1. 0 D D f (x 0)= f (x 0+D ) f (x 0).
2. .
3. . , f 0, = .
y = f (x) ( ). , f 0 () , () :
.
0 , , .
, 0, . 0, .
D 1 , f . Î D 1 , D 1. y = f (x) , .
.
: k , f 0, =tg a, a (.4.1).
f 0 , f 0.
г , f 0: .
: , , ; , , , .
: t, , .