Question 841696
{{{(4*pi)/9}}}<P>
The domain of sin is -pi/2 to pi/2.  5pi/9 falls outside that domain.  So, when taking the inverse function of the sin function for a value outside the sin function's domain, you have to pick the value inside the domain that has the same sin.<P>
sin(5pi/9) = sin(4pi/9)