IV. SOLVING TRIGONOMETRIC EQUATIONS OF FORM
Acosq + Bsinq = C
1. Express each of the following in the forms stated, where A, B, C, R are positive:
(a)
;
(b)
; ![]()
(c)
![]()
(d)
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2. (i) Express
in the form A.cos(q - a) where A>0, and hence solve the equation
for 0 < q < 2p.
(ii) Express
in the form
where R>0 and hence solve the equation
for 0 < x < 2p
3. (i) Express
in the form Acos(q + a) where A>0, hence state the greatest value of this expression and give the first positive value of q for which it occurs.
(ii) Express
in the form A.sin(x + b) where A>0 and hence state the greatest and least value of f(x). Show that ![]()
4. Express
in the form
, where R>0 and 0 < e < 2p. Hence:
(i) State the maximum and minimum values of
, and give the smallest positive value of q for which each of these occurs.
(ii) Solve the equation
= 1 for 0 < q < 2p
5. Express sinx + cosx in the form A.sin(x + a) where A>0 and hence solve the equation sinx + cosx = 1 for 0 < q < 2p
(i) What is the greatest value of sinx + cosx, and give the value of x in the interval 0 < q < 2p for which this occurs.
(ii) By an appropriate change of origin, sketch the graph of y = sinx + cosx for 0 < q < 2p.
6. If 4cosx - 3sinx = C.cos(x + e) for all x, find the values of C and e. Hence
(i) Find the roots of the equation 4cosx - 3sinx = 3 for 0 < q < 2p as accurately as possible.
(ii) Sketch the graph of y = 4cosx - 3sinx for 0 < q < 2p.
7. (i) Without calculus, state the greatest and least values of the expression
sint -
cost .
(ii) A particle moves along the x-axis so that its velocity v(t) at time t is given by
v(t) = cost +
sint. Obtain an expression for the displacement x(t) in terms of t.
Show that ![]()
(iii) By expressing sint =
cost in an appropriate form, solve the equation
sint -
cost =
for 0 < t < 2p.
8. Use the auxiliary angle method tto solve each of the following equations for 0 < q < 360.
(a)
(b)
(c) ![]()
9. By using the 't' method where
, solve the following equations for 0 < q < 360:
(a)
(b)
(c) ![]()