Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    12
    ReputationRep:
    Hi I've tried many times to integrate x(1+cosx) but I keep getting xsinx+cosx+c when it should be x^2/2 + xsinx + cosx + c I believe. So I'm missing x^2/2... would really appreciate if someone could help. Thanks
    Offline

    22
    ReputationRep:
    (Original post by jordanwu)
    Hi I've tried many times to integrate x(1+cosx) but I keep getting xsinx+cosx+c when it should be x^2/2 + xsinx + cosx + c I believe. So I'm missing x^2/2... would really appreciate if someone could help. Thanks
    Split (expand) into x + x cos x

    First term integrates to x^2/2.

    Second term use IBP.
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    (Original post by jordanwu)
    Hi I've tried many times to integrate x(1+cosx) but I keep getting xsinx+cosx+c when it should be x^2/2 + xsinx + cosx + c I believe. So I'm missing x^2/2... would really appreciate if someone could help. Thanks
    Zacken has given you the correct method. But it may also be a good idea if you post you working showing how you got xsinx+cosx+c.

    Then we can help you find your mistake.
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by Zacken)
    Split (expand) into x + x cos x

    First term integrates to x^2/2.

    Second term use IBP.
    Thanks!
    Offline

    22
    ReputationRep:
    (Original post by jordanwu)
    Thanks!
    No problem.

    Edit: 4 hours later, just saw notnek's reply, I agree - it'd be helpful for you to post your answer so we can identify what conceptual mistake you are making.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.