How can arctan(x) be expressed using logs?

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In summary, solving a trigonometric equation such as tan(y)=x can be done by setting it up in terms of logs, using methods like antidifferentiation or Euler's formula. The process involves solving a quadratic and manipulating the equation by multiplying both sides with e^x+e^-x.
  • #1
cragar
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my math teacher said that the arctan can be setup in terms of logs
does anyone know how to do this.
 
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  • #2
Solve tan(y)=x. (Prerequisite: you must know how to write tan(y) in terms of exponentials)

Other methods are possible (e.g. antidifferentiate f(x)=1/(1+x²)), but there are more technical details involved.
 
  • #3
can i use eulers formula to do it .

so would it be [(e^(ix)-e^(-ix)]/[(ie^(ix)+ie^(-ix))] = tan(x)
 
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  • #4
Correct.

You'll need to solve a quadratic in the process.
 
  • #5
what quadratic
 
  • #6
You have
[itex]tan x= \frac{e^x- e^{-x}}{e^x+ e^{-x}}= y[/itex]
First multiply on both sides of the equation by [itex]e^x+ e^{-x}[/itex].
Then multiply both sides o the equation by [itex]e^x[/itex]
 
  • #7
oh i see
 

Related to How can arctan(x) be expressed using logs?

1. What is the definition of arctan(x) in terms of logs?

Arctan(x) in terms of logs is defined as the inverse function of the tangent function when expressed in terms of logarithms. It represents the angle whose tangent is equal to x, where x is a real number.

2. How do you express arctan(x) in terms of natural logs?

To express arctan(x) in terms of natural logs, you can use the identity arctan(x) = ln((1+x)/(1-x))/2. This means that the natural log of the fraction (1+x)/(1-x) divided by 2 is equal to the arctan of x.

3. Can arctan(x) be written as a combination of other trigonometric functions?

Yes, arctan(x) can be written as a combination of other trigonometric functions. It is equal to 1/2 * ln((1+x)/(1-x)), which can be expressed in terms of the sine and cosine functions using the identities sin(x) = (1/2i)(e^ix - e^-ix) and cos(x) = (1/2)(e^ix + e^-ix).

4. How do you evaluate arctan(x) in terms of logs?

To evaluate arctan(x) in terms of logs, you can use a calculator or a table of logarithms. You can also use the Taylor series expansion for arctan(x): arctan(x) = x - x^3/3 + x^5/5 - x^7/7 + ... This allows you to approximate the value of arctan(x) by using the logarithms of the terms in the series.

5. What is the domain and range of arctan(x) in terms of logs?

The domain of arctan(x) in terms of logs is all real numbers except -1 and 1. The range is from -pi/2 to pi/2, or from -90 to 90 degrees. This is because the tangent function is undefined at -pi/2 and pi/2, and as the inverse of the tangent function, arctan(x) also cannot be defined at these values.

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