Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3

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In summary, the conversation discusses the integral ∫(sec^2 x tanx) dx from 0 to ∏/3 and the attempt to solve it using integration by parts. It is noted that there is a direct u-sub method to handle the integral, but the method used illustrates an important concept. The concept is that when performing integration by parts, the resulting integral may lead back to the original question, which can be solved using the equation I = B/2. This type of oscillatory behavior is important for many trigonometric and exponential integrals. The conversation concludes with the realization that this exact question came up in the math test.
  • #1
LocalStudent
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Homework Statement



∫(sec^2 x tanx) dx

the integral is from 0 to ∏/3

Homework Equations



I tried using integration by parts


The Attempt at a Solution



When I did integration by parts I got to this:

tan^2 x - ∫(sec^2 x tanx) dx (integral also from 0 to ∏/3)

which take you back to the question I started with.
 
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  • #2
Hint: Are there trigonometric identities that relate [itex]sec^{2}x[/itex] and [itex]tan^{2}x[/itex]?
 
  • #3
LocalStudent said:
When I did integration by parts I got to this:

tan^2 x - ∫(sec^2 x tanx) dx (integral also from 0 to ∏/3)

which take you back to the question I started with.
There is a direct u-sub to handle this integral, but the way you have done it does illustrate an important concept.

Suppose, I = ∫Adx and you perform integration by parts and get I = B - ∫Adx. Well, that second integral is, as you noted, what you started with. Thus, I = B - I and so 2I = B and thus, I=B/2.

That type of oscillatory behavior is very important for many trigonometric and exponential integrals.
 
  • #4
Jorriss said:
Suppose, I = ∫Adx and you perform integration by parts and get I = B - ∫Adx. Well, that second integral is, as you noted, what you started with. Thus, I = B - I and so 2I = B and thus, I=B/2.
integrals.

Thanks, that was really helpful. I hope I remember and notice it in my test.
 
  • #5
Jorriss said:
There is a direct u-sub to handle this integral, but the way you have done it does illustrate an important concept.

Suppose, I = ∫Adx and you perform integration by parts and get I = B - ∫Adx. Well, that second integral is, as you noted, what you started with. Thus, I = B - I and so 2I = B and thus, I=B/2.

That type of oscillatory behavior is very important for many trigonometric and exponential integrals.


Thanks again! This exact question came up in my math test :)
 

1. What is the equation for "Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3"?

The equation is ∫(sec^2 x tanx) dx from 0 to ∏/3.

2. How do you solve the integral for "Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3"?

To solve this integral, use the trigonometric identity sec^2 x = 1 + tan^2 x and then use substitution to change the integral into the form ∫(1 + tan^2 x) tanx dx. Then, use integration by parts to solve the integral.

3. What is the value of the integral for "Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3"?

The value of the integral is approximately 0.75.

4. Can you explain the steps to solving "Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3"?

First, use the trigonometric identity sec^2 x = 1 + tan^2 x to change the integral into the form ∫(1 + tan^2 x) tanx dx. Then, use u-substitution with u = tanx and du = sec^2 x dx to change the integral into the form ∫(1 + u^2) du. Use integration by parts with u = u and dv = 1 + u^2 to solve the integral. Finally, substitute back in u = tanx and solve for the limits of integration to get the final answer.

5. What is the significance of the limits of integration in "Integral Question: ∫(sec^2 x tanx) dx from 0 to ∏/3"?

The limits of integration, 0 and ∏/3, determine the range of values for x in the integral. In this case, the integral is being solved from 0 to ∏/3, which means that the area under the curve is being calculated within that specific range. It is important to have accurate limits of integration to get the correct value for the integral.

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