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)
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)