Trigonometry Problems
1. The displacement of a body is given by, s = 4sin (t + 30degrees), and
a force acting upon the body is given by, F = 7sin (t - 60degrees). If
the energy of the motion, E, at time t is the product Fs, show that E =
-14 cos (2t - 30 degrees).
2. The instantaneous current and voltage in an electric circuit are
given by
i = I cos 50pi*t
v = V cos (50pi*t + pi/6)
Determine an expression for the instantaneous power in the circuit, p =
iv, as the sum of two cosines.
3. If I is 3mA and V is 5 V, calculate the maximum value of p, giving
the answer in watts correct to three significant figures, and the first
positive value of t at which it occurs.
