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Find all degree solutions for the following cos4(theta)=-1

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bettyl1 | eNotes Newbie

Posted April 10, 2013 at 3:33 AM via web

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Find all degree solutions for the following cos4(theta)=-1

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oldnick | Valedictorian

Posted April 10, 2013 at 3:52 AM (Answer #1)

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`cos4 x=- 1`   means the argument of the function cos  is an angle  has cosin = -1

so angle wit cosin = -1 is only `pi` and congruent a round:

so:

`4x= pi+ 2k pi`  so that:  `x= pi/4 +k pi/2`  `k =0,1,2....`

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pramodpandey | College Teacher | Valedictorian

Posted April 10, 2013 at 4:03 AM (Answer #2)

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If you mean `cos(4theta)=-1`

then

`cos(4theta)=cos(pi)`

`4theta=2npi+-pi`

`theta=(np)/2+-pi/4` ,where  n is an integer.

If you mean `cos^4(theta)=-1`  ,then this problem has no solution.

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bettyl1 | eNotes Newbie

Posted April 10, 2013 at 4:11 AM (Answer #3)

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   means the argument of the function cos  is an angle  has cosin = -1

so angle wit cosin = -1 is only and congruent a round:

so:

  so that:   

Thank you! but what is the answer in degrees?

 

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