dierence The between dy and
y
dy is an approximation found by moving along the tangency.
y is the
dierence between two points on the actual function y = f (x). Given the
function
y = x2
the dierential is
dy = 2xdx
suppose x = 2 and = dx :01 then the dierential, dy is
dy = 2xdx = 2(2)(:01) = :04
The other change
y is given by
y
y
= (x + dx)2 x2
= (2:01)2 (2)2 = 0:0401
See the Graph for the dierence
y
y = x2
D
4.0401
y
C
dy
A
4
2
1
y
B
dx
2.01
x