Deduce that cos(2x)cox(x)+(1/2)sin(2x)cos(x)=√2 cos(x)cos(2x-(pi/4))

[KipWeit]

Hello, I am gonna send the two first questions of the exercise but I am stuck in 2 the second question

 

[apple2357]

Do you know any trig identities that you could make use of?
What do you know already? Look back through your notes and see if you can find some relationships? What you have tried so far? Post and maybe we can build on your ideas. Have you spotted the connection between part1 and part 2?

 

[KipWeit]

Do you know any trig identities that you could make use of?
What do you know already? Look back through your notes and see if you can find some relationships? What you have tried so far? Post and maybe we can build on your ideas. Have you spotted the connection between part1 and part 2?

These are the main identities that we use in class

 

[KipWeit]

Do you know any trig identities that you could make use of?
What do you know already? Look back through your notes and see if you can find some relationships? What you have tried so far? Post and maybe we can build on your ideas. Have you spotted the connection between part1 and part 2?

the rest

 

[apple2357]

So any thoughts? You have some useful stuff there - for example, some double angle identities? Your first screenshot has helpful identities.
But i would also look at the last screenshot which has cos(x+y)?

Looking at your original question.. can you expand cos(2x+pi/4)? Have a go and post back. I haven't actually done the question so don't know for sure but just suggesting ideas...

You do understand the purpose of the forum is not to do the work for you but help you along your journey? And you do appreciate this is the best way to help you?

 

[KipWeit]

So any thoughts? You have some useful stuff there - for example, some double angle identities? Your first screenshot has helpful identities.
But i would also look at the last screenshot which has cos(x+y)?

Looking at your original question.. can you expand cos(2x+pi/4)? Have a go and post back. I haven't actually done the question so don't know for sure but just suggesting ideas...

You do understand the purpose of the forum is not to do the work for you but help you along your journey? And you do appreciate this is the best way to help you?

I replaced f(x) with the results from the first question, and then I kept using different formulas but every time I get stuck, tomorrow I have an Exam so I am gonna try to solve it again

 

[apple2357]

Ok, so when you get a moment, post what you have done and where you got stuck.

 

[jonah2.0]

Deduce that
cos(2x)cox(x)+(1/2)sin(2x)cos(x)=√2 cos(x)cos(2x-(pi/4))

Hello, I am gonna send the two first questions of the exercise but I am stuck in 2 the second questionView attachment 26099

I'm assuming that the red part of your quoted post is a typo and that you meant to type
`cos(2x)cos(x)+1/2*sin(2x)cos(x)=sqrt(2)cos(x)cos(2x-pi/4)`

Considering that the left and right side of that alleged identity have different graphs, I'd say that you will be stuck there for a very long time. Check again in your book if you typed the correct identity.

KipWeit identity problem

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