SOLUTION: cos3xcos5x-cos7xcos9x=0

Question 891903: cos3xcos5x-cos7xcos9x=0
Answer by Edwin McCravy(20081) (Show Source): You can put this solution on YOUR website!



We use the product to sum formula on each term



Swap the factors in each product so the difference will be positive:

 













Use the doubla angle identity 
with , 







Multiply through by -1



Factor the left side:



Use zero-factor property:

,     

,     

,     
                    
,            
 








,     

Edwin

RELATED QUESTIONS
0 (answered by amruta)

0, 2, 0, 2,... (answered by Edwin McCravy)

6x^0+(6x)^0 (answered by longjonsilver)

x2+12x+0=0 (answered by checkley77)

sec 0 + sin... (answered by Jc0110)

2(0)�-2(0)= (answered by Alan3354)

Could we declare that 0+0, 0-0, 0x0, and 0/0 all equal 0?... (answered by venugopalramana)

x >... (answered by Nate)

(-10)^0 (answered by checkley71)