# Find all degree solutions for the following cos4(theta)=-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....`

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.

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?