Question

2cos2A+cosA-1=0. plz​

Answer 1

Step-by-step explanation:

The given equation is rewritten as 2 x^2 - x - 1 = 0, where x= cosine A.

2 x^2 - 2 x +x -1 = 0

2 x(x-1) - 1(x - 1) = 0

(x -1)(2 x - 1) = 0

x - 1 = o gives cosine A = 1 , or A = 0 or 360 n, where n is an integer.

2 x - 1= 0 gives , cosine A = 1 / 2. or A = 360 n + or - 30 degree.