How do I solve the equation cos^2(x) - 4*cos(x) + (7 / 4 ) < 0?

[JPC]

[SOLVED] Math - solving equation

Homework Statement

x belongs to Real numbers

Homework Equations

solving on paper
cos^2(x) - 4*cos(x) + (7 / 4 ) < 0

The Attempt at a Solution

no worthly attemps yet

 

[sara_87]

why don't you factorise it by using the completing the square thing or the ((-b)+or- (root(b^2) - 4ac) )/2a
...i think?

 

[EnumaElish]

To follow up on sara_87's post, let z = Cos(x). Now you have a quadratic equation (inequality) which you can solve for z.

Next time you have a similar question please post it under Pre-calculus Math.

 

[HallsofIvy]

Why in the world is this in "other Sciences"?

 

[JPC]

well, i didnt see simply 'math' section , only saw 'calculus math' , didnt see 'Precalculus Mathematics' since i didnt have much time to post, sorry for wrong section. Next time ill know where to post for these types of questions

and btw, thanks for your help, resolved it easily now

 

[berkeman]

Thread moved to Precalc Math.