solve trigonometric equation analytically

Calculus
Tutor: None Selected Time limit: 1 Day

solve for values of x for 0<= x < 2pi

cos^2 x +2 cos x +1 = 0

May 10th, 2015

we have : cos^2 x +2 cos x +1 = 0

 we know :  (x+1)²=x²+2x+1 

so : cos^2 x +2 cos x +1 = (cos(x) + 1)² = 0

so :  cos(x) + 1 =0 

so : cos(x) = -1 

so : cos(x) =  cos(pi)

so :  x= pi + 2Kpi 

or :  x= - pi + 2Kpi  

Good Luck my Friends 

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From your friend 

Karim 

May 10th, 2015

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