Calculus Volume 1

730

Chapter 6 | Applications of Integration

dy dx =

d dx

⎛ ⎝ log a x ⎞ ⎠

⎛ ⎝ ln x ln a

⎞ ⎠

= d

dx ⎛ ⎝ 1

⎞ ⎠ d

dx (ln

x )

=

ln a

= 1

· 1 x

ln a

= 1 x

.

ln a

Theorem 6.21: Derivatives of General Logarithm Functions Let a >0. Then, d dx log a x = 1 x ln a .

Example 6.40 Calculating Derivatives of General Exponential and Logarithm Functions

Evaluate the following derivatives: a. d dt ⎛ ⎝ 4 t ·2 t 2 ⎞ ⎠

⎛ ⎝ 7 x 2 +4 ⎞ ⎠

d dx log 8

b.

Solution We need to apply the chain rule as necessary. a. d dt ⎛ ⎝ 4 t ·2 t 2 ⎞ ⎠ = d dt ⎛ ⎝ 2 2 t ·2 t 2 ⎞ ⎠ = d dt ⎛ ⎝ 2 2 t + t 2 ⎞

2

⎠ =2 2 t + t

ln(2)(2+2 t )

⎛ ⎝ 7 x 2 +4 ⎞

d dx log 8

(14 x )

⎠ = 1 ⎛ ⎝ 7 x 2 +4 ⎞

b.

⎠ (ln8)

6.40

Evaluate the following derivatives:

t 4

a. d

dt 4

⎛ ⎝ x 2 +1

⎞ ⎠

d dx log 3

b.

Example 6.41 Integrating General Exponential Functions

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