This discussion is now closed.

Check out other Related discussions

Never ending Integration

Mighty Grandiose Noble Knight

1

Integrate sin2x sin x

If you use by parts method, you keep going on forever.

So how do you do it?

Reply 1

refref

You mean you get to a point where you have the integral of sin2xsinx on both sides of your equation?

Treat it as a single variable, call it A or something and move it to the other side to get 2 (integral)sin2xsinx and then divide both sides by 2.

Reply 2

technicolour

3

=2\sin ^2x \cos x

Any ideas now?

Spoiler

Reply 3

Mighty Grandiose Noble Knight

OP

1

ShortRef

You mean you get to a point where you have the integral of sin2xsinx on both sides of your equation?

Treat it as a single variable, call it A or something and move it to the other side to get 2 (integral)sin2xsinx and then divide both sides by 2.

Yes.

Don't get what you mean though (2nd paragraph).

Reply 4

Mighty Grandiose Noble Knight

OP

1

technicolour

=2\sin ^2x \cos x

Any ideas now?

Spoiler

Oh I see. I mean the question had

=2\sin ^2x \cos x

but I changed it because in my other thread from yesterday this Cambridge mathematician said not to treat it as

\sin ^3x

. However, I know why now...

Thanks mate.

Reply 5

refref

Mighty Grandiose Noble Knight

Yes.

Don't get what you mean though (2nd paragraph).

\int {\sin{2x}\sin{x}} = something - \int {sin{2x}\sin{x}}

2\int {\sin{2x}\sin{x}} = something

Or change sin2x into 2sinxcosx

Mighty Grandiose Noble Knight

Oh I see. I mean the question had

=2\sin ^2x \cos x

but I changed it because in my other thread from yesterday this Cambridge mathematician said not to treat it as

\sin ^3x

. However, I know why now...

Thanks mate.

I think that was a slightly different question?

Yeh that was when you had sin^2x on its own, this is different because you have a cosx, so now you can do this one by recognition.

Reply 6

Mighty Grandiose Noble Knight

OP

1

ShortRef

\int {\sin{2x}\sin{x}} = something - \int {sin{2x}\sin{x}}

2\int {\sin{2x}\sin{x}} = something

Or change sin2x into 2sinxcosx

But then if you use by parts you are going to end up with something similar hence it goes on forever.

*I know which method to use now.

Thanks for the help.

Never ending Integration

Related discussions

Latest

Trending

Trending

Articles for you