If 4cos^2(x)-3cos(x)=0 what is cos(x)?

1 Answer
Alan P.
Sep 22, 2016

cos(x)=0color(white)("XX")orcolor(white)("XX")cos(x)=3/4

Explanation:

It might be easier to think about this if you (temporarily) replace cos(x) with some variable, for example k

Then we have
color(white)("XXX")4k^2-3k=0

which can be factored as
color(white)("XXX")k(4k-3)=0

Which implies
color(white)("XXX"){:(k=0,color(white)("XX")orcolor(white)("XX),4k-3=0),(,,rarrk=3/4):}

But k is simply cos(x)

So
color(white)("XXX"){:(cos(x)=0,color(white)("XX")orcolor(white)("XX"),cos(x)=3/4):}

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