I take 22/7 to be π..
2sin(...)=-1, so (...)=sin-1(-½)=7π/6 or 11π/6. The general solution is these angles +2πn where n is an integer.
⅕(10π+C)=7π/6+2πn or 11π/6+2πn,
2π+C/5=7π/6+2πn or 11π/6+2πn,
C/5=7π/6+2πn or 11π/6+2πn,
C=35π/6+10πn or 55π/6+10πn.