How would you simplify this logarithmic expression?

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Discussion Overview

The discussion focuses on the simplification of the logarithmic expression $\displaystyle \frac{1}{5}\ln|\sin5x|+\frac{1}{5}\ln|\csc5x-\cot5x|$. Participants explore various methods and steps involved in simplifying this expression, including factoring and combining logarithms.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests factoring out the $\frac{1}{5}$ from the expression.
  • Another participant proposes using the property of logarithms that allows the combination of logs: $\ln a + \ln b = \ln (ab)$.
  • Several participants arrive at the expression $\frac{1}{5} \left[ \ln |\sin (5x) \cdot (\csc (5x) - \cot (5x) )| \right]$.
  • Further simplifications lead to the expression $\frac{1}{5} \ln |1 - \cos (5x)|$.
  • There is a mention of an additional simplification to $\frac{1}{5}\ln\left|2\sin^2\! \frac{5x}{2}\right|$.
  • One participant notes that the modulo sign can be removed in the last step since the expression is positive.

Areas of Agreement / Disagreement

Participants generally agree on the steps to simplify the expression, but there are variations in the final forms presented and whether the modulo sign can be removed. No consensus is reached on a single final expression.

Contextual Notes

Some steps in the simplification process may depend on specific assumptions about the values of $x$ and the behavior of the trigonometric functions involved.

paulmdrdo1
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how would you simplify this

$\displaystyle \frac{1}{5}\ln|\sin5x|+\frac{1}{5}\ln|\csc5x-\cot5x|$

please explain.
 
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Re: simplification of expression

What have you tried?
 
Re: simplification of expression

Ackbach said:
What have you tried?

i just factored out the 1/5 and I'm stucked.
 
Re: simplification of expression

Hello Paul! Notice you can factor the $1/5$, yielding $$\frac{1}{5} \left[ \ln |\sin 5x | + \ln |\csc 5x - \cot 5x| \right],$$ and from here use that $\ln a + \ln b = \ln (ab)$. Consequently

$$\frac{1}{5} \left[ \ln |\sin 5x | + \ln |\csc 5x - \cot 5x| \right] = \frac{1}{5} \left[ \ln |\sin (5x) \cdot (\csc (5x) - \cot (5x) )| \right] = \frac{1}{5} \left[ \ln |1 - \cos (5x)| \right].$$

Cheers. :D
 
Re: simplification of expression

Hello, paulmdrdo!

\text{Simplify: }\:\tfrac{1}{5}\ln|\sin5x|+\tfrac{1}{5}\ln|\csc5x-\cot5x|
\begin{array}{ccc}\text{Factor:} & \tfrac{1}{5}\big(\ln|\sin5x| + \ln|\csc5x - \cot5x|\big) \\ \\ \text{Combine logs:} & \tfrac{1}{5}\ln|\sin5x(\csc5x - \cot5x)| \\ \\ \text{Distribute:} & \tfrac{1}{5}\ln|\sin5x\csc5x - \sin5x\cot5x| \\ \\ \text{Simplify:} & \tfrac{1}{5}\ln|1-\cos5x| \\ \\ \text{Further?} & \tfrac{1}{5}\ln\left|2\sin^2\! \tfrac{5x}{2}\right| \end{array}
 
Re: simplification of expression

soroban said:
Hello, paulmdrdo!


\begin{array}{ccc}\text{Factor:} & \tfrac{1}{5}\big(\ln|\sin5x| + \ln|\csc5x - \cot5x|\big) \\ \\ \text{Combine logs:} & \tfrac{1}{5}\ln|\sin5x(\csc5x - \cot5x)| \\ \\ \text{Distribute:} & \tfrac{1}{5}\ln|\sin5x\csc5x - \sin5x\cot5x| \\ \\ \text{Simplify:} & \tfrac{1}{5}\ln|1-\cos5x| \\ \\ \text{Further?} & \tfrac{1}{5}\ln\left|2\sin^2\! \tfrac{5x}{2}\right| \end{array}

In the last step we can remove modulo sign as it positive
 

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