Hello,

this equation has to be solved in 2 steps:

1. solve for cos(t)

2. solve for t

to 1.:

Substitute y = cos(t) and your equation becomes:

2y² - y - 1 = 0

which wil give: y = 1 or y = -0.5

to 2.:

Plug in the values:

cos(t) = 1 ===> t = 0 or t = 2pi

cos(t) = -0.5 ===> t = (2/3)pi or t = (4/3)pi

EB