$$\lim_{t \to \infty}\left(a \cos{\left(t \right)}\right) = \left\langle -1, 1\right\rangle a$$
$$\lim_{t \to 0^-}\left(a \cos{\left(t \right)}\right) = a$$
More at t→0 from the left$$\lim_{t \to 0^+}\left(a \cos{\left(t \right)}\right) = a$$
More at t→0 from the right$$\lim_{t \to 1^-}\left(a \cos{\left(t \right)}\right) = a \cos{\left(1 \right)}$$
More at t→1 from the left$$\lim_{t \to 1^+}\left(a \cos{\left(t \right)}\right) = a \cos{\left(1 \right)}$$
More at t→1 from the right$$\lim_{t \to -\infty}\left(a \cos{\left(t \right)}\right) = \left\langle -1, 1\right\rangle a$$
More at t→-oo