Integrating Tan Squared Sec Squared: Solving the Challenging Integral

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In summary, the conversation discusses finding the integral of tan^2xsec^2xdx by using the equation tan^2x=sec^2x-1 and a substitution method. The final solution is \int{(1+u^2)du}.
  • #1
Mentallic
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Homework Statement


Find [tex]\int{tan^2xsec^2xdx}[/tex]


Homework Equations


[tex]tan^2x=sec^2x-1[/tex] (1)


The Attempt at a Solution


Using (1): [tex]\int{(sec^4x-sec^2x)dx}[/tex]

Now, [tex]\int{sec^4xdx}-\int{sec^2xdx}=\int{sec^4xdx}-tanx+c[/tex]

I can't figure out how to solve [tex]\int{sec^4xdx}[/tex] though.
 
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  • #2
The derivative of tan(x) is sec^2(x). Mentallic, this is a simple substitution. u=tan(x).
 
Last edited:
  • #3
Oh yeah... ugh I feel like such an idiot.

[tex]u=tanx[/tex]

[tex]\int{sec^4xdx}=\int{(1+u^2)du}[/tex]

Thanks Dick.
 
  • #4
Mentallic said:
Oh yeah... ugh I feel like such an idiot.

[tex]u=tanx[/tex]

[tex]\int{sec^4xdx}=\int{(1+u^2)du}[/tex]

Thanks Dick.

Sure, but why don't you use that substitution in the original integral?
 
  • #5
Oh, you mean like [tex]\int{u^2du}[/tex] ? Yeah because I love to make things harder for myself
 

Related to Integrating Tan Squared Sec Squared: Solving the Challenging Integral

1. What is the formula for integrating tan^2xsec^2x?

The formula for integrating tan^2xsec^2x is ∫tan^2xsec^2x dx = tanx + C.

2. How do you solve the integral of tan^2xsec^2x?

To solve the integral of tan^2xsec^2x, you can use the trigonometric identity tan^2x + 1 = sec^2x. This will allow you to rewrite the integral as ∫(sec^2x - 1)sec^2x dx. From there, you can use the power rule to integrate and then substitute back in the original values for tanx and secx.

3. Is there a shortcut for integrating tan^2xsec^2x?

Yes, there is a shortcut for integrating tan^2xsec^2x called the reduction formula. It states that ∫tan^nxsec^mxdx = (tan^(n-1)xsec^(m-1)x)/(n-1) + (m-1)/n * ∫tan^(n-2)xsec^(m-2)xdx. By using this formula, you can reduce the power of tanx and secx until you reach a point where you can easily integrate.

4. Can you use substitution to integrate tan^2xsec^2x?

Yes, you can use substitution to integrate tan^2xsec^2x. A common substitution is u = tanx, which will allow you to rewrite the integral as ∫u^2sec^2xdx. From there, you can use the trigonometric identity sec^2x = 1 + tan^2x to further simplify the integral and solve it using integration by parts.

5. What are the common mistakes to avoid when integrating tan^2xsec^2x?

One common mistake to avoid when integrating tan^2xsec^2x is forgetting to use the trigonometric identity tan^2x + 1 = sec^2x. This is a crucial step in simplifying the integral and can lead to incorrect solutions if overlooked. Another mistake is not applying the power rule correctly, which can result in incorrect values for the integral. It is important to double-check your work and make sure all steps are followed accurately.

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