Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
$$4 \sin^{3}{\left(5 x \right)} = 0$$
Solve this equationThe points of intersection with the axis X:
Analytical solution$$x_{1} = 0$$
$$x_{2} = \frac{\pi}{5}$$
Numerical solution$$x_{1} = 50.2654784282671$$
$$x_{2} = -79.7964422180974$$
$$x_{3} = 30.1593030386965$$
$$x_{4} = -99.9026586531636$$
$$x_{5} = -23.8761047798227$$
$$x_{6} = 62.2035457264783$$
$$x_{7} = 98.0176847884392$$
$$x_{8} = -3.76990603457228$$
$$x_{9} = 13.1946807694429$$
$$x_{10} = -54.0353822177094$$
$$x_{11} = -39.5840782677381$$
$$x_{12} = 32.0442319686978$$
$$x_{13} = -65.973454466631$$
$$x_{14} = 65.9734545620738$$
$$x_{15} = -87.9646054416544$$
$$x_{16} = 67.8584044664188$$
$$x_{17} = 76.0265334791505$$
$$x_{18} = 42.0973292858246$$
$$x_{19} = -91.7345095170872$$
$$x_{20} = -25.7610568725516$$
$$x_{21} = 21.9911516322427$$
$$x_{22} = 84.1946958447672$$
$$x_{23} = -47.7522077559909$$
$$x_{24} = 28.2743276110676$$
$$x_{25} = 6.28317687213508$$
$$x_{26} = 43.9823031772716$$
$$x_{27} = -43.9823031577186$$
$$x_{28} = -76.0265333838752$$
$$x_{29} = -15.7079737629519$$
$$x_{30} = -74.1415834601493$$
$$x_{31} = 20.1061836459268$$
$$x_{32} = 72.2566292972523$$
$$x_{33} = -93.6194741889191$$
$$x_{34} = 48.3805137463582$$
$$x_{35} = 94.2477801894259$$
$$x_{36} = -98.0176847689387$$
$$x_{37} = 74.1415950490631$$
$$x_{38} = 89.8495385744551$$
$$x_{39} = 52.1504496308635$$
$$x_{40} = -96.132723464583$$
$$x_{41} = -57.8052920993563$$
$$x_{42} = 45.867264469363$$
$$x_{43} = -89.8495383079016$$
$$x_{44} = 87.9646057279071$$
$$x_{45} = -45.8672485280578$$
$$x_{46} = -21.9911516309942$$
$$x_{47} = -30.1592988122439$$
$$x_{48} = -52.1504493462834$$
$$x_{49} = -69.7433586481537$$
$$x_{50} = -37.6991242681696$$
$$x_{51} = 54.035382503596$$
$$x_{52} = -1.88496093911439$$
$$x_{53} = 40.2123953230364$$
$$x_{54} = 26.3893724569146$$
$$x_{55} = 0$$
$$x_{56} = -67.858392888113$$
$$x_{57} = 4.39823701644331$$
$$x_{58} = 18.2212447146651$$
$$x_{59} = 96.132739407901$$