1. 9 cos x =9
cos x = 1
x = + - arccos 1 + 2pin, n ∈ Z
X = +- pi n, n ∈ Z
2. -2cosx = 0
cos x = 0
x= p/2 m, m ∈ Z
3. - 6 sin x = 0
sin x = 0
x = pl, l ∈ Z
4 . sin 2 x = 1
2x = p/2 + 2pk , k ∈ Z
x = p/4 + 4 pk, k ∈ Z
x = 3p/4 + 4 pk, k ∈Z
5. sin 2x = 1/2
2x = p/6 +2 pn, n ∈ Z
x= p/12 + 4pn, n ∈ Z
x= 11p/12 + 4 pn, n ∈ Z
6. 2 cos x = 1
cos x= 1/2
x= p/3 + 2pk, k ∈ Z
x= - p/3+ 2pk, k ∈ Z
7. 2 cos x = -√3
cos x= -√3/2
x = 2p/3 + 2pl, l ∈ Z
x= -2p/3 + 2 pl, l ∈ Z
8. 2 sinx = √2
sinx = √2/2
x= p/4+ 2pk, k ∈ Z
x= 3p/4 + 2pk, k ∈ Z
9. cos x/2 = √2/2
x/2 = + - p/4 + 2p n, n ∈ Z
x = + - p/2 + pn, n ∈ Z