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How do you solve ${cos}^{2} x + 2 cos x + 1 = 0$ $cos^2x+2 cos x+1=0$ ?

1 Answer

Jun 24, 2016

$x = pi + 2k pi, {k = 0, pm1, pm2, pm3,...}$

Explanation:

$(cos x + 1)^2=cos^2x+2cosx+1=0$

then

$cos x+1=0$

$x = pi + 2k pi, {k = 0, pm1, pm2, pm3,...}$

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