# Solving a trig equation #2

• February 16th 2011, 03:04 PM
powerduffgirL
Solving 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!
• February 16th 2011, 03:12 PM
pickslides
Do you mean solve this equation for $\displaystyle x$ ?

If so make $\displaystyle u=\cos x$ and solve the quadratic $\displaystyle 2u^2-5u+2=0$
• February 16th 2011, 03:59 PM
skeeter
Quote:

Originally Posted by powerduffgirL
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

... recommend you find out the difference between identities and conditional equations.