2. Derivative
The instantaneous Rate of Change of a
function.
Application
Derivatives are met in many engineering
and science problems, especially, when
modelling the behavior of moving
objects. Like in;
Gaming , designing, etc.
4. CONSTANT | RULE
The derivative of a constant function f(x) = c is 0. That is, f’(x) = 0. This can also be
written as :
𝑑𝑓
𝑑𝑥
=
𝑑
𝑑𝑥
(c) = 0.
Examples:
o If f(x) =
1
2
then f’(0) = 0.
oIf y = −π, then
𝑑𝑦
𝑑𝑥
=
𝑑
𝑑𝑥
(-π) = 0.
5. CONSTANT
MULTIPLE
| RULE
If c is any constant, then
𝑑
𝑑𝑥
(cf(x)) = cf’(x).
Example:
If y = 2x then,
𝑑
𝑑𝑥
2𝑥 = 2
𝑑
𝑑𝑥
𝑥 = 2(1) .
f’(x) = 2.
6. Addition and Subtraction |Rule
If f and g are differentiable functions, then
Addition Rule
𝑑
𝑑𝑥
𝑓 + 𝑔 =
𝑑
𝑑𝑥
𝑓 +
𝑑
𝑑𝑥
𝑔
Subtraction Rule
𝑑
𝑑𝑥
𝑓 − 𝑔 =
𝑑
𝑑𝑥
𝑓 −
𝑑
𝑑𝑥
𝑔
8. PRODUCT |
RULE
If f and g are differentiable functions, then
𝑑
𝑑𝑥
𝑓 × 𝑔 = 𝑓
𝑑
𝑑𝑥
𝑔 + 𝑔
𝑑
𝑑𝑥
𝑓 .
Example:
If f(x) = 𝑥2
𝑒 𝑥
, then
𝑥2
𝑑
𝑑𝑥
𝑒 𝑥 + 𝑒 𝑥
𝑑
𝑑𝑥
𝑥2 .
𝑥2(𝑒 𝑥) + 𝑒 𝑥(2x).
9. Power | RULE
If n is any number as a power, then
𝑑
𝑑𝑥
(𝑥 𝑛 ) = n (𝑥 𝑛−1 )
𝑑
𝑑𝑥
(x) .
Examples:
oIf f(x) = 𝑥4 then f’(x) = 4𝑥3(1)= 4 𝑥3 .
o If f(x) = 𝑥−45 then f’(x) = -45𝑥−46(1)= -45 𝑥−46 .
10. QUOTIENT|
RULE
If f and g are differentiable functions, then
𝑑
𝑑𝑥
(
𝑓
𝑔
) =
𝑔
𝑑
𝑑𝑥
𝑓 −𝑓
𝑑
𝑑𝑥
(𝑔)
𝑔 ^2
Example:
If
𝑑
𝑑𝑥
(
𝑥2
𝑥+5
),
(𝑥+5)
𝑑
𝑑𝑥
𝑥2 −𝑥2 𝑑
𝑑𝑥
(𝑥+5)
(𝑥+5)^2
F’(x)=
2𝑥 −𝑥2
(𝑥+5)
=
𝑥(2−𝑥)
(𝑥+5)
11. The Chain Rule
If f(u) is differentiable at the point
u = g(x) and g(x)
is differentiable at x, then the
composite function:
[f (g(x))] = f’(g(x))g’(x).