For the following exercises, solve with the methods shown in this section exactly on the interval [0,2pi ).
40. cos(6x)-cos(3x)=0
For the following exercises,solve with the methods shown in this section exactly on the interval [0,2n)
33.sin3xcos6x-cos3xsin6x=-0.9
34.sin6xcos11x-cos6xsin11x=-0.1
35.cos2xcosx+sin2xsinx=1
36.6sin2t+9sint=0
37.9cos20=9cos-4
38.sin2t=cost
39.cos2t=sin t
40.cos6xcos3x=0