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-   -   1+cos(2theta)+cos(4theta)+cos(6theta)=4cos(theta)c os(2theta)cos(3theta) (https://www.askmehelpdesk.com/showthread.php?t=813875)

  • Jul 9, 2015, 01:47 PM
    aldo63
    1+cos(2theta)+cos(4theta)+cos(6theta)=4cos(theta)c os(2theta)cos(3theta)
    Help identify identity
  • Jul 12, 2015, 04:20 AM
    sidit
    1+cos2@+cos4@+cos6@
    =cos4@+cos2@ +1+cos6@
    =2cos4+2/2 @.cos4-2/2 @+1+2cos**3@-1
    [email protected]@ + 2cos**3@
    =2cos3@(cos@ +cos3@)
    2cos3@(2cos3+1/2 @.cos3-1/2 @)
    [email protected]@.cos@
    [email protected]@.cos@
    [email protected]@.cos3@
  • Jul 19, 2015, 10:33 AM
    kreysiz
    use the identities:-
    1) cos(2pi) = 1
    2) cos2x + cos2y = 2*cos(x+y)*cos(x-y)

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