Question

I need to solve for x

Answer 1

Even without the one written c is suppost to represent 1 in these

Answer 2

Solution is {0,2π3,4π3}

Step-by-step explanation:

2cos2x−cosx−1=0 can be written as

2cos2x−2cosx+cosx−1=0

or 2cosx(cosx−1)+1(cosx−1)=0

or (2cosx+1)(cosx−1)=0

∴ either 2cosx+1=0 i.e. cosx=−12 and in the interval [0,2π) x=2π3 or 4π3

or cosx−1= i.e. cosx=1 and in given interval x=0.