1. Complex Numbers &
Trig Identities
(i) Express cos 2 and sin 2 in terms of cos and sin
2. Complex Numbers &
Trig Identities
(i) Express cos 2 and sin 2 in terms of cos and sin
cos 2 i sin 2 cos i sin
2
3. Complex Numbers &
Trig Identities
(i) Express cos 2 and sin 2 in terms of cos and sin
cos 2 i sin 2 cos i sin
cos 2 2i sin cos sin 2
2
4. Complex Numbers &
Trig Identities
(i) Express cos 2 and sin 2 in terms of cos and sin
cos 2 i sin 2 cos i sin
cos 2 2i sin cos sin 2
By equating real and imaginary parts
2
5. Complex Numbers &
Trig Identities
(i) Express cos 2 and sin 2 in terms of cos and sin
cos 2 i sin 2 cos i sin
cos 2 2i sin cos sin 2
By equating real and imaginary parts
2
cos 2 cos 2 sin 2
sin 2 2 sin cos
7. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
3
8. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
3
9. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
3
10. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
3
sin 3 3sin cos 2 sin 3
11. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
3
sin 3 3sin cos 2 sin 3
3sin 1 sin 2 sin 3
3sin 3sin 3 sin 3
3sin 4sin 3
12. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
3
sin 3 3sin cos 2 sin 3
3sin 1 sin 2 sin 3
3sin 3sin 3 sin 3
3sin 4sin 3
cos3 cos3 3sin 2 cos
13. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
3
sin 3 3sin cos 2 sin 3
3sin 1 sin 2 sin 3
3sin 3sin 3 sin 3
3sin 4sin 3
cos3 cos3 3sin 2 cos
cos3 3 1 cos 2 cos
cos3 3cos 3cos3
4cos3 3cos
14. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
sin 3
tan 3
sin 3 3sin cos 2 sin 3
cos3
3sin 1 sin 2 sin 3
3sin cos 2 sin 3
3
3
cos3 3sin 2 cos
3sin 3sin sin
3
3sin 4sin 3
cos3 cos3 3sin 2 cos
cos3 3 1 cos 2 cos
cos3 3cos 3cos3
4cos3 3cos
15. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
sin 3
tan 3
sin 3 3sin cos 2 sin 3
cos3
3sin 1 sin 2 sin 3
3sin cos 2 sin 3
3
3
cos3 3sin 2 cos
3sin 3sin sin
3
3sin cos 2 sin 3
3sin 4sin
cos3
3
2
cos3 3sin 2 cos
cos3 cos 3sin cos
cos3
3
2
cos 3 1 cos cos
3sin sin 3
cos3 3cos 3cos3
cos cos3
3
cos3 3sin 2
4cos 3cos
3
cos cos 2
3
16. (ii) Express sin3 ,cos3 and tan 3 in terms of sin ,cos and tan
cos3 i sin 3 cos i sin
cos3 3i sin cos 2 3sin 2 cos i sin 3
By equating real and imaginary parts
sin 3
tan 3
sin 3 3sin cos 2 sin 3
cos3
3sin 1 sin 2 sin 3
3sin cos 2 sin 3
3
3
cos3 3sin 2 cos
3sin 3sin sin
3
3sin cos 2 sin 3
3sin 4sin
cos3
3
2
cos3 3sin 2 cos
cos3 cos 3sin cos
cos3
3
2
cos 3 1 cos cos
3sin sin 3
3
cos3 3cos 3cos3
cos cos3 3tan tan
3
cos3 3sin 2
1 3tan 2
4cos 3cos
3
cos cos 2
3
17. (iii) Show that x cos
9
is a solution to 8 x 3 6 x 1 0
18. (iii) Show that x cos
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
9
is a solution to 8 x 3 6 x 1 0
19. (iii) Show that x cos
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
let x cos
9
is a solution to 8 x 3 6 x 1 0
20. (iii) Show that x cos
9
is a solution to 8 x 3 6 x 1 0
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
let x cos
2(4cos3 3cos ) 1 0
2cos3 1 0
1
cos3
2
21. (iii) Show that x cos
9
is a solution to 8 x 3 6 x 1 0
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
let x cos
2(4cos3 3cos ) 1 0
2cos3 1 0
1
cos3
2
5 7
3 , ,
3 3 3
5 7
, ,
9 9 9
22. (iii) Show that x cos
9
is a solution to 8 x 3 6 x 1 0
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
let x cos
2(4cos3 3cos ) 1 0
2cos3 1 0
1
cos3
2
5 7
3 , ,
3 3 3
5 7
, ,
9 9 9
5
7
x cos ,cos ,sin
9
9
9
23. (iii) Show that x cos
9
is a solution to 8 x 3 6 x 1 0
8 x3 6 x 1 0
2(4 x 3 3 x) 1 0
let x cos
2(4cos3 3cos ) 1 0
2cos3 1 0
1
cos3
2
5 7
3 , ,
3 3 3
5 7
, ,
9 9 9
5
7
x cos ,cos ,sin
9
9
9
x cos
9
is a solution
28. (iii) Evaluate cos
9
cos
2
5
cos
9
9
5
7
x cos ,cos ,sin
are the roots of 8x 3 6 x 1 0
9
9
9
1
8
5
7 1
cos cos cos
9
9
9 8
but cos
7
2
cos
9
9
2
5
1
cos
cos cos
9
9
9
8
product of roots
29. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
30. iv
1
1
n
If z cos i sin , find z n and z n
z
z
z n cos n i sin n
n
31. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
32. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
33. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
1
z n 2 cos n
z
n
zn
1
2i sin n
n
z
34. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
1
z n 2 cos n
z
n
v
Express cos3 in terms of cos n
zn
1
2i sin n
n
z
35. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
1
z n 2 cos n
z
n
v
Express cos3 in terms of cos n
3
3
z 1
2 cos
z
3 1
3
3
8 cos z 3 z 3
z z
zn
1
2i sin n
n
z
36. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
1
z n 2 cos n
z
n
v
Express cos3 in terms of cos n
3
3
z 1
2 cos
z
3 1
3
3
8 cos z 3 z 3
z z
1
1
z 3 3 3 z
z
z
zn
1
2i sin n
n
z
37. iv
1
1
n
If z cos i sin , find z n and z n
z
z
n
z n cos n i sin n
1
z n cos n i sin n
zn
cos n i sin n
cos is even function cos x cos x
sin is odd function sin x sin x
1
z n 2 cos n
z
n
v
zn
1
2i sin n
n
z
Express cos3 in terms of cos n
3
3
z 1
2 cos
z
3 1
3
3
8 cos z 3 z 3
z z
1
1
z 3 3 3 z
z
z
8cos3 2cos3 6cos
1
3
cos cos 3 cos
4
4
3