Calculating Volume by Rotating y = e^x * sin(x) Around the x-Axis

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SUMMARY

The discussion focuses on calculating the volume generated by rotating the function y = e^x * sin(x) around the x-axis for the interval x ∈ [0, π]. The integral for this volume is expressed as π ∫ e^(2x) * sin²(x) dx. Participants suggest using the identity sin²(x) = 1/2 - (1/2)cos(2x) to simplify the integral, leading to two separate integrals that can be solved using integration by parts. The conversation emphasizes the necessity of applying integration techniques effectively to arrive at the solution.

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  • Understanding of integral calculus
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  • Knowledge of trigonometric identities, specifically sin²(x)
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I'm supposed to find the volume of the figure that appears by rotating the follwing around the x-axis:
y = e^x \cdot \sin (x) & x \in \left[ {0,\left. \pi \right]} \right.
This means (I think) that the function needs to be to the second power and multiplied by Pi in an integral. So the integral becomes
<br /> \pi \int {e^{2x} \cdot \sin ^2 (x)dx} <br />
I need hints on how to solve this integral, I've tried integration by parts but not really gotten anywhere...am I on the right track?
 
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here is a hint, maybe change sin squared into something more friendly.
 
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I tried to change it into 1-cos2x = 2(sinx)^2, but I didn't find it to make it any easier...was that what you thought about?
 
yes, change (sinx)^2 = 1/2 - (1/2)cos2x. multiply your e function through and you will have 2 integrals that can be solved. the integral with (e^2x)(1/2 cos 2x) is going to need parts twice.
 
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I do believe you might be on to something there 1800bigk...thx!
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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