How to use the factor formuale for integration ?

Hello there, someone said that instead of using the addition formuale , you could use the factor formulae (P+Q) to make integration easier to do...but i dont know how to do this and is currently struggling with it...pls help me do this example:


THANKS in advance !


2sin2xsin5x

2sin2xsin5x

$\cos B - \cos A =2 \sin \dfrac{A+B}{2} \sin \dfrac{A-B}{2}$

is given in the formula booklet

hello there pls can u talk in terms of P and Q since that is the way it is laid out in the formula sheets and hence i would find that way easier....
cheerios!

I thought you did edexcel

yes of course I do edexcel!

yes of course I do edexcel, sorry noticed now in the formuale sheet that it is in terms of A and B but in the TEXTBOOK in terms of P and Q,,pls can u do P and Q ...sorry for rude lang...

If you're not going to be bothered to learn how to apply the formulas in your formula packet, you might as well ignore them.

But anyways:

Let P=(A+B)/2 and Q=(A-B)/2

Find A and B, and your formula for 2sinPsinQ will come out.

hello do what do we do after this stage:
A+B/ 2 = 5
A-B / 2 = 2

Therefore adding together gives, A= 7 and B= 3

then cos7x-cos3x ....BUT THEN WHAT I AM REALLY STUCK WITH IS HOW TO ADJUST THE CONSTANTS IN FRONT....

Are you saying that you do not know that

$\int \cos kx dx = -\frac{1}{k}\sin kx$

Are you saying that you do not know that

$\int \cos kx dx = -\frac{1}{k}\sin kx$

btw , you have got that wrong...no minus sign

and i am not talking about that

on here we have got

2sin2xsin5x
what do we have to do with the two>

You have used the 2 already

If you hadn't then you would just have a 2*the answer

how do u say that i ave used the 2 already>>>

Go back over your work ... you must have used the 2 ... it is in the formula

but isnt there a MINUS sign in the formula?

yes, there are a few (2 or 3 depending on how you write it)

which one in particular are you worried about