You can
put this solution on YOUR website!from cos^2T + 2cosT +1 = 0, let x=cosT, therefore

. You can factorise this (or put it in the formula)...
factorised...(x+1)(x+1)=0, so x=-1, so cosT = -1.
Now you need to tell me the range of theta, so you can find the answers.
cosT = 1 is 0 degrees, and -1 is 180 degrees.
cheers
Jon.