Differentiating :calculus theory

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Homework Help Overview

The problem involves verifying the identity arctan(x) + arctan(1/x) = π/2 using calculus theory, specifically through differentiation. Participants are exploring the relationship between the functions involved and their derivatives.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Some participants attempt to differentiate the left-hand side of the identity and express it in terms of tangent functions. Others question the origin of certain expressions and seek clarification on the differentiation process.

Discussion Status

Participants are actively discussing the differentiation of the identity and exploring the implications of their findings. Some guidance has been offered regarding the differentiation process, and there is acknowledgment of the need to specify conditions for the variable x.

Contextual Notes

There is a hint provided in the original problem to differentiate the left side, and some participants note confusion regarding the steps involved in the differentiation. The discussion also touches on the behavior of the function across its domain, particularly for x ≠ 0.

chapsticks
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Homework Statement




Verify the identity:

arctanx + arctan(1/x)=∏/2

using calculus theory.
(Hint: Differentiate the left hand side of the identity)

Homework Equations



?

The Attempt at a Solution


is this correct?

tan(arctanx + arctan(1/x))
= [tan(arctan(x)) + tan(arctan(1/x))][1 - tan(arctan(x))*tan(arctan(1/x))]

= [x + 1/x]/[1 - x*1/x] = (x + 1/x)/0 = oo

tan pi/2 = oo
 
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mmm... they wanted you to do this:
[tex]\frac{1}{1+x^2}+ etc...[/tex]
 
where did that come from I'm confused??
 
chapsticks said:

Homework Statement




Verify the identity:

arctanx + arctan(1/x)=∏/2

using calculus theory.
(Hint: Differentiate the left hand side of the identity)

Homework Equations



?

The Attempt at a Solution


is this correct?

tan(arctanx + arctan(1/x))
= [tan(arctan(x)) + tan(arctan(1/x))][1 - tan(arctan(x))*tan(arctan(1/x))]

= [x + 1/x]/[1 - x*1/x] = (x + 1/x)/0 = oo

tan pi/2 = oo

Start by using the hint, which is to differentiate the left side.
 
f'(x)=1/(1+x2) + -1/(x2+1) =0

for all x≠0

function is constant on domain

is this right?
 
chapsticks said:
f'(x)=1/(1+x2) + -1/(x2+1) =0

for all x≠0

function is constant on domain

is this right?

Yes, it is. I guessing they meant to specify x>0. Now just pick a nice value of x to put into figure out what the constant is.
 

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