Respuesta :

TREKKER

Answer:

60, 90, 270, 300 degrees

Step-by-step explanation:

a = cos(x)

2(a^2) + a = 0

a(2a + 1) = 0

a = 0 OR 1/2

so...

cos(x) = 0 OR cos(x) = 1/2

x = 90 or 270 OR x = 60 or 300