integration question (1 Viewer)

[fullonoob]

not ^3
me failed

 

[hscishard]

Is it possible to do this?

So then it can be 1/Sec(2x) x Tan3x + C

 

[Trebla]

 

[seanieg89]

Absolute values inside the logarithm trebla.

And hscishard, no you cannot. You cannot in general take non-constant factors of the integrand to the outside of the integral.

 

[Pwnage101]

Yeh, integrating sec is one of those you have to remember to multiply out by (sec + tan).

 

[Drongoski]

I posted my solution yesterday morning but for some reason it disappeared.

 

[hscishard]

Absolute values inside the logarithm trebla.

And hscishard, no you cannot. You cannot in general take non-constant factors of the integrand to the outside of the integral.

Ooo I see.

For which maths course do we use absolute values in logs? I know it's not in 2unit...

 

[seanieg89]

I'm not sure which courses don't require it, but it is technically correct. For example f(x) := 1/x is integrable over the interval [-2,-1] but our primitive F(x) = ln (x) is undefined for non-positive x. We need to use the primitive F(x) = ln |x| (this works because f is an odd function).

 

[duckcowhybrid]

I believe only 4U strictly requires it, but it wouldn't hurt to do it in every exam.

 

[fullonoob]

yeah only 4u requires it, but do you get marks deducted if you miss out the absolute value?
btw was bos down for like 4 days? or did mine just stuff up

 

[Drongoski]

yeah only 4u requires it, but do you get marks deducted if you miss out the absolute value?
btw was bos down for like 4 days? or did mine just stuff up

looks like it.

It's been taking ages to come on.

Several of my posted solutions got lost, including one for coeff of term in x^4 for binomial thm problem.

 

[Trebla]

I don't think you would lose marks for not placing the absolute values in the logarithms. People have always done it without them every year (even the standard integral table doesn't use it). If they did penalise this, then it would be mentioned in the notes from the marking centre.