(a) Using a trig identity, write $x(t) = -3\cos\!\left(4t\right)+\sin\!\left(4t\right)$ using only one cosine function.

$x(t) =$ help (formulas)

(b) Using a trig identity, write $x(t) = 3\cos\!\left(4t\right)+\sin\!\left(4t\right)$ using only one cosine function.

$x(t) =$ help (formulas)

(c) Using a trig identity, write $x(t) = e^{-5t}\!\left(-3\cos\!\left(4t\right)+\sin\!\left(4t\right)\right)$ using only one cosine function in your answer.

$x(t) =$ help (formulas)

Hint: