Answer:
27
Step-by-step explanation:
x=pi*n/2+1/2arctan(7/5)
5sin(2x)=7cos(2x)
5tan(2x)=7/5
2x=pi*n+arctan(7/5)
x=pi*n/2+1/2arctan(7/5) for n e Z
0;3,6;9................................