(a) Using a trig identity, write x(t) = -3 cos(7t) + 2 sin(7t) using only one cosine function. x(t) = sqrt(13)*cos(7t-146.3099) help (formulas) (b) Using a trig identity, write x(t) = 3 cos(7t) + 2 sin(7t) using only one cosine function. x(t) = sqrt(13)*cos(7t-33.69006753) help (formulas) (c) Using a trig identity, write x(t) =e5t (-3 cos(7t) + 2 sin(7t)) using only one cosine function in your answer. x(t) = e^(-5t)*sqrt(13)*cos(7t-146.3099) BEB help (formulas)