Solve the equation

(a) \(2\lvert \sin x\rvert=1\) for \(-\pi\le x\le \pi\) radians,

(b) \(3\tan(2y+15^\circ)=1\) for \(0^\circ\le y\le 180^\circ\),

(c) \(3\operatorname{cot}^2 z=\operatorname{cosec}^2 z-7\operatorname{cosec} z+1\) for \(0^\circ\le z\le 360^\circ\).