Hi,
If cos(a+b)=cosacosb-sinasinb and
if cos(a- b)=cosacosb+sinasinb then cosacosb=?

Question

Hi,
If cos(a+b)=cosacosb-sinasinb and
if cos(a- b)=cosacosb+sinasinb then cosacosb=?

anonymous · Answer

I think the answer is like 1/2[something] but I dont know where to start!

anonymous · Answer

Has to do with trig formulas but I need some help.

jhonyy9 · Answer

so if cos(a+b)=cosacosb -sinasinb
and cos(a-b)=cosacosb +sinasinb so than if you assum these will get 
      ------------------
    cos(a+b +cos(a-b)=2cosacosb and now just divide both sides by 2 and will get 

  cos(a+b)+cos(a-b)
----------------- = cosacosb
              2

hope so much that is understandably sure rigth 

good luck

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