Question

Find all solutions in the interval [0, 2π).

cos^2 x + 2 cos x + 1 = 0

Answer 1

i got this far and now im lost. my book doesnt explain it too well.
(cos x +1)(cos x +1)
cos x=-1 cos x =-1

Answer 2

ok so use your calculator to get the angle(s) whose cosine is -1

Answer 3

or you can get it from unit circle

Answer 4

x = pi

Answer 5

ok. this is where i rushed past sum key concepts in my book.lol. im lost how do i get angles whose cos is -1?