is it necessary (1 Viewer)

[hup]

to put | | when using ln

 

[b3kh1t]

to put | | when using ln

Do you mean brackets like ln(2x) or what??

 

[kaz1]

not when the function in the log is an absolute positive function like x²+1

 

[hup]

so if you have like
you have to say ln |x-1| ?

 

[cutemouse]

Well, you can use absolute values. If you don't and you get a negative value inside the function and you recombine the expression using log laws then you should get a positive value inside the log function (ie. the -ve's will cancel).

 

[apollo1]

so if you have like
you have to say ln |x-1| ?

the solutions in the Maths association of NSW 4U past paper book have the absolute value signs so im guessing they are required. my school never really bothered though.

 

[Omnipotence]

You do need absolute signs. I lost marks for it, because I did brackets instead.

 

[D94]

Yes, for integration/volume/area questions. Essentially, integration is finding the area underneath a curve, so you will have cases where there is a negative value in the logarithm which would make it impossible, so using absolute value signs are necessary.

If it's just a value, ie. ln(2), then it's not required.

 

[rawrence]

Yes, but you don't use it in mechanics question. It's important to leave it out from those solutions.

Otherwise, integrands and other algebraic applications should have it.

But I really don't think markers will deduct without them, unless of course it alters the actual solution which it rarely does unless your evaluation has like "ln(-1)", then you'd probably realise you need those abs values.

 

[cutemouse]

But I really don't think markers will deduct without them, unless of course it alters the actual solution which it rarely does unless your evaluation has like "ln(-1)", then you'd probably realise you need those abs values.

You will never get ln(-1) as your final answer. You might get something like ln(-1) - ln(-2), which combines to be ln(-1/-2) = ln(1/2), ie. the negative signs cancelling out after applying log laws...

 

[Shadowdude]

In school, didn't do it. At university, they drum it into you that you must always use the absolute value signs. ALWAYS.

So whichever, for now.