Calculus I Assignment # 5

This assignment covers
Exponential and Log Derivatives
Logarithmic Differentiation

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QUESTIONS

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Find the derivative

1) 2)

3) 4)

5) y = x ln x

6) y = 5 3x + (3x) 5.
7) 8) y = (x² + 1) 2x .

9) y = x² e - cot 2x .

10) y = x sin 5x

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SOLUTIONS

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Find the derivative

1) Rewrite f (x) using log rules

2) Rewrite f (x) using log rules

3)


so y' = 2x

4) Rewrite f (x) using log rules

5) use logarithmic differentiation it's
a variable to a variable exponent.

now, y = x ln x t ln y = (ln x) 2 or ln 2 x.

6) y' = 3(5 3x) ln 5 + 15(3x) 4.

7)

8) use logarithmic differentiation it's
a variable to a variable exponent.

ln y = 2x ln (x² + 1)

so

so

9) we use product rule here

y' = 2x e - cot 2x + 2x² csc² 2x e - cot 2x .

with some factoring,
y' = 2x e - cot 2x (1 + x csc² 2x) .

10) use logarithmic differentiation it's
a variable to a variable exponent.

ln y = sin 5x (ln x)

Using product rule again we get

so

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