Help solving problem

Well I need to prove that it's true, its trig and I don't even know where to start lol. Just a practice problem I'm working on to get better at trig identities and trig proofs.
 
Scrutinize said:
Well I need to prove that it's true, its trig and I don't even know where to start lol. Just a practice problem I'm working on to get better at trig identities and trig proofs.
Click to expand...
So think about the following:

15/2 = 7.5

6 = 7.5 - 1.5

9 = 7.5 + 1.5

7 = 7.5 - 0.5

8 = 7.5 + 1.5

How do these information relate to your given problem and

How can you use these information and the hint I gave you towards solving your problem?
 
Well I know I have to simplify all the sin functions at the top into one and all of the cos functions in the denominator into one, but I still don't really understand how. sin(A + B) + sin(A - B) = 2*sin(A)*cos(B) is how I'll have to do it, but I'm not sure what A is and what B is in the context of my problem. Cause inside the trig functions there is no addition or subtraction?
 
Scrutinize said:
Well I know I have to simplify all the sin functions at the top into one and all of the cos functions in the denominator into one, but I still don't really understand how. sin(A + B) + sin(A - B) = 2*sin(A)*cos(B) is how I'll have to do it, but I'm not sure what A is and what B is in the context of my problem. Cause inside the trig functions there is no addition or subtraction?
Click to expand...
Are you doing these problems with pencil and paper or just staring at the screen?

sin(6x) + sin (9x) = sin(7.5x - 1.5x) + sin(7.5x + 1.5x)

continue....
 
Ah I see, is there a rule for cos(A+B) + cos(A - B) so I can simplify the denominator as well?

PS: Thanks a lot for the help!
 
Scrutinize said:
Cause inside the trig functions there is no addition or subtraction?
Click to expand...
As SK has hinted at least twice yo need to see the addition and subtraction signs on your own.
6 = 7-1 and 8 = 7+1 for example (don't use these numbers as SK's numbers are better).
Now please show us your work with the excellent hint provided.
 
Jomo said:
As SK has hinted at least twice yo need to see the addition and subtraction signs on your own.
6 = 7-1 and 8 = 7+1 for example (don't use these numbers as SK's numbers are better).
Now please show us your work with the excellent hint provided.
Click to expand...
Yes, I already said I understood that. I was asking if there was a rule for cos(A+B) + cos(A - B). I already simplified all of the sin functions. And correct the hint was excellent and helped me a lot.
 
Just expand cos(A+B) and cos(A-B) and add the results together and you'll have the rule.
Please try this and show us your results. Thanks
 
Please write out the for well-known expansions:

[math]sin(\alpha + \beta)[/math] =
[math]sin(\alpha - \beta)[/math] =
[math]cos(\alpha + \beta)[/math] =
[math]cos(\alpha - \beta)[/math] =

You don't have to be dependent on memorization.
 
Got it, attached is all my messy work. Thanks so much for the help everyone!
 

Attachments

  • Math Export.pdf
    1.6 MB · Views: 4
You must log in or register to reply here.
Top