2cos^2x-1=0,x=5pi/4?

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Answer 1 · 2018-05-03T20:35:47

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if your question was

$2cos^2(x)-1=0$

The solution:

hit the two side by $1/2$

$cos^2(x)-1/2=0$

$cos^2(x)=1/2$

$cos(x)=+-1/sqrt2$

$x=45$ when $cosx=1/sqrt2$

$x=315$ when $cosx=1/sqrt2$

$x=135$ when $cosx=-1/sqrt2$

$x=225$ when $cosx=-1/sqrt2$

or you mean

$2cos^2(x-1)=$

$cos^2(x-1)=$

$x=(5pi/4)=225$

$cos^2(225-1)=$

$cos^2(224)=0.34127$