Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    Heres my working out, and was hoping someone could check it out ?
    http://imgur.com/EHpu4yC

    The question is dx / [ROOT (1-x^2)]

    I can't use partial fractions as the questions wants me to use substitution
    Offline

    0
    ReputationRep:
    I'll give you a hint: When you see a 1+/-x^2 on the denominator, it's usually a trigonometric/hyperbolic trig substitution you need to make. Knowing that, can you think of something such that 1 - (something)^2 = (something else)^2? If you can, the root will drop out and you should see the whole integral simplify
    Offline

    19
    ReputationRep:
    (Original post by T-GiuR)
    Heres my working out, and was hoping someone could check it out ?
    http://imgur.com/EHpu4yC

    The question is dx / [ROOT (1-x^2)]

    I can't use partial fractions as the questions wants me to use substitution
    You cannot use partial fractions here even if you wanted to.

    after your substitution you must get

    ∫cosθ/√(1-sin2θ) dθ
    Offline

    18
    ReputationRep:
    (Original post by T-GiuR)
    Heres my working out, and was hoping someone could check it out ?
    http://imgur.com/EHpu4yC
    In the 2nd line you have (incorrectly) got rid of the square root, incorrectly divided by the derivative of the substitution term when you should have multiplied, and done the division wrong (*).

    It's kind of impressive, in a perverse kind of fashion...

    (*) Well, I think that's what you've done - when so much goes wrong in so little space it's kind of hard to be sure.
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by TeeEm)
    You cannot use partial fractions here even if you wanted to.

    after your substitution you must get

    ∫cosθ/√(1-sin2θ) dθ
    I tried it again, and got this ?
    http://imgur.com/cy9Wv6a
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by DFranklin)
    In the 2nd line you have (incorrectly) got rid of the square root, incorrectly divided by the derivative of the substitution term when you should have multiplied, and done the division wrong (*).

    It's kind of impressive, in a perverse kind of fashion...

    (*) Well, I think that's what you've done - when so much goes wrong in so little space it's kind of hard to be sure.
    Tried it again and got this ?
    http://imgur.com/cy9Wv6a
    Offline

    18
    ReputationRep:
    (Original post by T-GiuR)
    Tried it again and got this ?
    http://imgur.com/cy9Wv6a
    Yes that's fine.
    Offline

    19
    ReputationRep:
    (Original post by T-GiuR)
    I tried it again, and got this ?
    http://imgur.com/cy9Wv6a
    the answer is correct now


    PS:
    Please do not take it the wrong way.
    The answer is correct but the way your work is presented is not very clear and you are running the risk if your answer is incorrect not to get any credit (even if the mistake is minute)
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by TeeEm)
    the answer is correct now


    PS:
    Please do not take it the wrong way.
    The answer is correct but the way your work is presented is not very clear and you are running the risk if your answer is incorrect not to get any credit (even if the mistake is minute)
    Thank you, and I completely understand.
    I didn't have any A4 paper next to me so I had to do it in a small diary
    Offline

    19
    ReputationRep:
    (Original post by T-GiuR)
    Thank you, and I completely understand.
    I didn't have any A4 paper next to me so I had to do it in a small diary
    no worries
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: December 2, 2014

University open days

  • Heriot-Watt University
    School of Textiles and Design Undergraduate
    Fri, 16 Nov '18
  • University of Roehampton
    All departments Undergraduate
    Sat, 17 Nov '18
  • Edge Hill University
    Faculty of Health and Social Care Undergraduate
    Sat, 17 Nov '18
Poll
Have you ever experienced bullying?
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

Equations

Best calculators for A level Maths

Tips on which model to get

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

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

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