What is the exact value of cos(–60º)? Negative StartFraction StartRoot 3 EndRoot Over 2 EndFraction
Negative one-half
One-half
StartFraction StartRoot 3 EndRoot Over 2 EndFraction

pls

Step-by-step explanation:

cos(-60°) = cos(60°) = ½

let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3

then the equation is (x-x₁)(x-x₂) = 0

if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.

step-by-step explanation:

you can see that a=1 (there is just an x²)

b = (-5 -2√7 + 2√7 - 5)/3 = -10/3

c = -2√7)/3 ) * (-5+2√7)/3) = -1/3

so your answer is 3x^2 – 10x – 1 = 0