integration (1 Viewer)

[fullonoob]

i got it a bit after i posted xD
can you do root (x^2-9) ^-1/2 and then integrate normally?
is it still correct?

 

[gurmies]

Go nuts - it's in your standard integrals though =)

 

[cutemouse]

Um, why have you quoted hyperbolic functions? :O

 

[gurmies]

I dunno, we've finished them a few weeks ago and wanted to see if I could still remember ^^

 

[Aquawhite]

Big boys use implicit differentiation.

It's been a while since I used implicit... Not many examples have needed it that I've done lately... I didn't even recognize to do it then, 3U made me lazy

Yea, it would have saved a little time... and I guess looked better and smarter too; but in a case of failing logic, I hit up my roots.

 

[fullonoob]

integrate sin5xcos3x dx
need someone to check answer xD
mines prob bs
i got -cos8x/16 - cos2x/4 + c

 

[mirakon]

integrate sin5xcos3x dx
need someone to check answer xD
mines prob bs
i got -cos8x/16 - cos2x/4 + c

If you used the sums to products and products to sum method then it probably is right

 

[cutemouse]

integrate sin5xcos3x dx

 

[Rezen]

jm01, check your solution i think you made a mistake (after second use of integration by parts).

using the sums to product identity;

 

[cutemouse]

jm01, check your solution i think you made a mistake (after second use of integration by parts).

Yep. I forgot the 1/3. Oh well, I just was just showing an alternative method that I thought of on the spot.

LateX is hard to read when typing

 

[fullonoob]

woot i got it right xD

 

[fullonoob]

integrate cos@/sin^5@ d@

 

[fullonoob]

 

[cutemouse]

 

[fullonoob]

lol @ me i shouldnt do maths at night xD

 

[fullonoob]

show that sin@ = 2t / 1+t^2

 

[cutemouse]

show that sin@ = 2t / 1+t^2

you mean if tan(x/2)=t, where x=/= pi right?

Just draw a right angled triangle (ie. a basic triad) and use the appropriate trig double angle formula.

 

[fullonoob]

says show so you cant just draw it. i can't remember doubl angles
i need help with :
Use the substitution x = 2sin@ to evaluate integral between 1 and 0 x^2/ [root(9-x^2)]^3 dx

 

[kaz1]

says show so you cant just draw it. i can't remember doubl angles
i need help with :
Use the substitution x = 2sin@ to evaluate integral between 1 and 0 x^2/ [root(9-x^2)]^3 dx

Have you tried it? It's a very simple substitution, the only slightly complex thing is the trig identity in the denominator.

 

[fullonoob]

is the answer 2ln root 3 -1??
btw how do you know what to substitute if it doesnt tell you for trig
and please help with the show sin one