Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

C4 - How would you integrate this?

∫ 2 sin 3x sin 2x dx.

Multiple methods pls and the simplest way
thanks !

Can be done by parts or use of factor formulae. ie.

\displaystyle \cos A - \cos B = -2\sin \left ( \frac{A+B}{2} \right ) \sin \left ( \frac{A-B}{2} \right )

.

(edited 8 years ago)

OP

This was the markscheme way of doing it: = ∫ (cos x − cos 5x) dx
idk how they went from the original integral to this....

Look at my post above

Original post by Someboady

This was the markscheme way of doing it: = ∫ (cos x − cos 5x) dx
idk how they went from the original integral to this....

OP

Original post by B_9710

Can be done by parts or use of factor formulae. ie.

\displaystyle \cos A - \cos B = -2\sin \left ( \frac{A+B}{2} \right ) \sin \left ( \frac{A-B}{2} \right )

.

Ah... why have I never seen this formulae before :/

OP

Original post by B_9710

Look at my post above

Is the formula given (Edexcel) or do I have to memorise that *cries* or can I derive it in an exam?

Original post by Someboady

Is the formula given (Edexcel) or do I have to memorise that *cries* or can I derive it in an exam?

You can derive it but it's easier just to remember it. There's 4 factor formula's you need to know although apparently it's not tested the factor formulae. But best to know I think.

OP

Original post by B_9710

You can derive it but it's easier just to remember it. There's 4 factor formula's you need to know although apparently it's not tested the factor formulae. But best to know I think.

Ah they're given in the formula book yesss, thanks a bunch dude :smile:

:smile:

would never have known about them :/ kinda scary

I got it using a triple angle formula, a double angle formula then a substitution. It should be pretty simple from here

Kevin De Bruyne

Original post by Someboady

∫ 2 sin 3x sin 2x dx.

Multiple methods pls and the simplest way
thanks !

Just to add, have a look at your formula booklet (online). For Edexcel I suspect that it is in C3.

Quick Reply

Latest

Trending

Trending

Articles for you

Course, age and previous study

How to save (and earn) more money while you're at university

How to save (and earn) more money while you're at university

Studying for a law degree; the differences between MLaw and LLB courses

Studying for a law degree; the differences between MLaw and LLB courses

Medicine entry requirements – five key things to know

Medicine entry requirements – five key things to know