Could anyone help on this trig identity? I have a quiz tomorrow and am unsure on this one.

2 cos squared x- 5 cosx+ 2= 0

Any help is appreciated!

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- Feb 16th 2011, 03:04 PMpowerduffgirLSolving a trig equation #2
Could anyone help on this trig identity? I have a quiz tomorrow and am unsure on this one.

2 cos squared x- 5 cosx+ 2= 0

Any help is appreciated! - Feb 16th 2011, 03:12 PMpickslides
Do you mean solve this equation for $\displaystyle \displaystyle x$ ?

If so make $\displaystyle \displaystyle u=\cos x$ and solve the quadratic $\displaystyle \displaystyle 2u^2-5u+2=0$ - Feb 16th 2011, 03:59 PMskeeter