I think we have a problem here. I think that this is the equation you mean

if it is this has No REAL solutions(It does have complex solutions). If you think about it the sine function described above has an amplitude of 1 so its max value will be one. So there is no way that it can ever reach 30.

As far as the CAST rule it tells us what trig functions are positive and where.

It starts in quadrant three where C=cosine is positive. Moving counter clockwise to quadrant one A= All are positive. Next to quadrant two S=sine is positive. Finally, to quadrant three where tangent is positive.

I hope this helps.