F'(x)=sin((pi (e^x)) /2) and f(0)=1

  • Context: Undergrad 
  • Thread starter Thread starter Punkyc7
  • Start date Start date
  • Tags Tags
    E^x
Click For Summary

Discussion Overview

The discussion revolves around the problem of finding the value of the function f(2) given that f'(x) = sin((pi (e^x)) / 2) and f(0) = 1. Participants explore methods of integration and numerical approximation to solve the problem.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant integrates f'(x) but questions the result when evaluating at x=2, suggesting that none of the provided answer choices match.
  • Another participant questions whether an analytical approach is necessary, noting difficulty in finding a primitive function for sin(pi e^x / 2) and suggests numerical integration instead.
  • A third participant challenges the correctness of the integration performed by the first participant and suggests that the sign and approximate size of the right-hand side could help eliminate some answer choices.
  • One participant recommends using Euler's method for numerical approximation, assuming access to a calculator.
  • Another participant proposes using the Taylor series expansion around 0, providing an approximation based on the third derivative and suggesting further computation up to the fifth derivative for better accuracy.

Areas of Agreement / Disagreement

Participants express differing opinions on the method of integration, with some advocating for numerical methods while others suggest series expansion. There is no consensus on the best approach or the correctness of the initial integration.

Contextual Notes

Participants highlight the difficulty in finding an exact integral for the given function, and there are unresolved questions regarding the accuracy of the integration methods discussed.

Punkyc7
Messages
415
Reaction score
0
f'(x)=sin((pi (e^x)) /2) and f(0)=1 then f(2)= ?

so i integrate and get -(1/((pi/2)*e^x)) cos((pi (e^x)) /2)+ 1=1

when i plug two into that i don't get any of the answers listed

a)-1.819
b) -.843
c.) -.819
d) .157
e) 1.157
 
Physics news on Phys.org


Are you supposed to do this analytically? Because I can't really find a primitive function for sin(pi e^x / 2). I can do the integration numerically though, and get one of the listed answers.
 


What he said. Your "integrate" is incorrect. Instead of finding an exact formula, can you tell by looking at the sign and approximate size of the RHS that all but one of the answers is ruled out?
 


If you have a calculator (which I can assume by the answer choices), try Euler's method.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
1K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 4 ·
Replies
4
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K