Answer:
a. 11/5 pi; -9/5 pi
Step-by-step explanation:
Coterminal angles are those which have a common terminal side. For example 30° is coterminal with −330° and 390° (see figure).
From the example we can see that the following expressions must be fulfilled:
positive angle - reference angle = 360°
reference angle - negative angle = 360°
where positive angle is 390°, reference angle is 30° and negative angle is -330°. In this problem reference angle is pi/5. Also, we have to change 360° for its equivalent in radians, i. e., 2 pi. So,
positive angle - pi/5 = 2 pi
positive angle = 2 pi + pi/5
positive angle = 11/5 pi
pi/5 - negative angle = 2 pi
negative angle = pi/5 - 2 pi
negative angle = -9/5 pi
Assuming you mean f(t) = g(t) × h(t), notice that
f(t) = g(t) × h(t) = cos(t) sin(t) = 1/2 sin(2t)
Then the difference quotient of f is
Recall the angle sum identity for sine:
sin(x + y) = sin(x) cos(y) + cos(x) sin(y)
Then we can write the difference quotient as
or
(As a bonus, notice that as h approaches 0, we have (cos(2h) - 1)/(2h) → 0 and sin(2h)/(2h) → 1, so we recover the derivative of f(t) as cos(2t).)