to solve this equation -3 cos t = 1 in the interval form 0 ≤ theta ≤ 2n by using the inverse function of cosine. -3 cos t = 1 cos t = -1 / 3 then using the inverse function arc cosine or cos^ -1 t = cos ^ -1 ( - 1 / 3 ) t = 1.91 is the value of theta that is within the range of 0 ≤ theta ≤ 2n i hope this can help you and feel free to ask for clarifications