How to simplify the expression:

cos(4x)cos(3x) - sin(4x)cos(3x)

Please guide me through, not the answer:)

Question

How to simplify the expression:

cos(4x)cos(3x) - sin(4x)cos(3x)

Please guide me through, not the answer:)

anonymous · Answer

To simplify this expression, Am I looking for cos(theta +beta)?

experimentx · Answer

yes ... cos(4x+3x)

anonymous · Answer

ok, Is the answer to this a number? or is it something like the previous question?

phi · Answer

cos(4x+3x)= cos(4x)cos(3x)- sin(4x)sin(3x)
It would be nice.  Are we sure of the question?

anonymous · Answer

Is the answer 0.6087?

campbell_st · Answer

simplify the expression

cos(3x)(cos(4x) - sin(4x))

then use 

cos(4x) =8cos^4(x) - 8cos^2(x) +1

sin(4x) = 4sin(x)cos(x) -8sin^3(x)cos(x)

cos(3x) = 4cos^3(x) - 3cos(x)

phi · Answer

@open   How are you getting numbers?  If you were asked what is the sin(x) what would you answer?  btw, are you positive you typed the question correctly?

anonymous · Answer

Yeah the question is typeed correctly

campbell_st · Answer

and cos(4x + 3x) = cos(4x)cos(3x) - sin(4x)sin(3x) and not the question asked

anonymous · Answer

Youre right, its cos at the end, not sin

phi · Answer

The simplest I see is to factor out cos(3x)
cos(3x)(cos(4x)-sin(4x)