-2sin(5x/2)sin(3x/2)=0
sin(5x/2)=0
5x/2=πk,k∈z
x=2πk/5,k∈z
0≤2πk/5≤4π
0≤2k≤20
0≤k≤10
k=0 x=0
k=1 x=2π/5
k=2 x=4π/5
k=3 x=6π/5
k=4 x=8π/5
k=5 x=2π
k=6 x=12π/5
k=7 x=7π/5
k=8 x=16π/5
k=9 x=9π/5
k=10 x=4π
sin(3x/5)=0
3x/5=πn,n∈z
x=5πn/3
0≤5πn/3≤4π
0≤5n≤12
0≤n≤12/5
k=0 x=0
k=1 x=5π/3
k=2 x=10π/3