Join TSR now and get all your revision questions answeredSign up now
    Offline

    1
    ReputationRep:
    (Original post by Jammy4410)
    just finally checked that doing it using the substitution involving cosh will get to the same correct answer but being able to simplify to the answer is almost impossible to spot unless you work back from the answer
    Your and my methods both give the answer as:

    {1 \over A} \sqrt{x} \sqrt{Ax - B} + {B \over 2 A^{3/2}} \cosh^{-1} \Big( {2Ax - B\over B} \Big) + const

    Is that not the form the answer is given in?
    • Thread Starter
    Offline

    3
    ReputationRep:
    (Original post by steve44)
    Your and my methods both give the answer as:

    {1 \over A} \sqrt{x} \sqrt{Ax - B} + {B \over 2 A^{3/2}} \cosh^{-1} \Big( {2Ax - B\over B} \Big) + const

    Is that not the form the answer is given in?

    The answer they gave:

    has the same first term but the second term is:
    B/A^(1.5) times log (root[A]root[Ax-B]+Aroot[x])
    • Thread Starter
    Offline

    3
    ReputationRep:
    \ (B/A^ \frac{3}{2}) ln(\sqrt {A} \sqrt {Ax-B}+A\sqrt {x})
    Offline

    1
    ReputationRep:
    (Original post by Jammy4410)
    \ (B/A^ \frac{3}{2}) ln(\sqrt {A} \sqrt {Ax-B}+A\sqrt {x})

    I see what you mean by if you dont know the answer it is difficult to spot it.
    You use \cosh^{-1} x = \ln [x + \sqrt{x^2-1}] and have to note that

    (\sqrt{A} \sqrt{Ax-B} + A \sqrt{x})^2 = AB \Big( {2Ax - B \over B} + \sqrt{\Big( {2Ax - B \over B} \Big)^2-1} \Big).
 
 
 
Poll
Which web browser do you use?
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

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.