El gráfico de la función cruce el eje X con f = 0
o sea hay que resolver la ecuación:
$$\left(\sin{\left(x \right)} + \sin{\left(2 x \right)}\right) - \sin{\left(3 x \right)} = 0$$
Resolvermos esta ecuaciónPuntos de cruce con el eje X:
Solución analítica$$x_{1} = 0$$
$$x_{2} = - \frac{2 \pi}{3}$$
$$x_{3} = \frac{2 \pi}{3}$$
$$x_{4} = \pi$$
Solución numérica$$x_{1} = -59.6902604182061$$
$$x_{2} = 96.342174710087$$
$$x_{3} = 31.4159494987662$$
$$x_{4} = -2.0943951023932$$
$$x_{5} = -21.9911485751286$$
$$x_{6} = -96.342174710087$$
$$x_{7} = 41.8879020478639$$
$$x_{8} = -92.1533845053006$$
$$x_{9} = 39.7935069454707$$
$$x_{10} = -29.3215314335047$$
$$x_{11} = -50.2654136196456$$
$$x_{12} = 54.4542726622231$$
$$x_{13} = -39.7935069454707$$
$$x_{14} = -94.2477142538712$$
$$x_{15} = 48.1710873550435$$
$$x_{16} = -41.8879020478639$$
$$x_{17} = 34.5575191894877$$
$$x_{18} = 8.37758040957278$$
$$x_{19} = 94.2477801894817$$
$$x_{20} = -54.4542726622231$$
$$x_{21} = 79.5870138909414$$
$$x_{22} = -8.37758040957278$$
$$x_{23} = 0$$
$$x_{24} = 98.4365698124802$$
$$x_{25} = -77.4926187885482$$
$$x_{26} = 50.2654784092342$$
$$x_{27} = -69.115098346029$$
$$x_{28} = 87.964606307459$$
$$x_{29} = -65.9734457253857$$
$$x_{30} = -90.0589894029074$$
$$x_{31} = 85.870199198121$$
$$x_{32} = 35.6047167406843$$
$$x_{33} = 58.6430628670095$$
$$x_{34} = -31.4159995782527$$
$$x_{35} = 12.5663007403281$$
$$x_{36} = 59.6902604182061$$
$$x_{37} = 92.1533845053006$$
$$x_{38} = 14.6607657167524$$
$$x_{39} = 6.28317668366371$$
$$x_{40} = 72.2566310325652$$
$$x_{41} = 2.0943951023932$$
$$x_{42} = -85.870199198121$$
$$x_{43} = -72.2566310325652$$
$$x_{44} = 46.0766922526503$$
$$x_{45} = 56.5486011335469$$
$$x_{46} = -6.28311308944196$$
$$x_{47} = 28.2743338823081$$
$$x_{48} = -37.6991249557468$$
$$x_{49} = 100.530901600679$$
$$x_{50} = 10.471975511966$$
$$x_{51} = -46.0766922526503$$
$$x_{52} = -52.3598775598299$$
$$x_{53} = 18.849561985036$$
$$x_{54} = 21.9911485751286$$
$$x_{55} = -79.5870138909414$$
$$x_{56} = -15.707963267949$$
$$x_{57} = -43.9823032309153$$
$$x_{58} = 65.9734457253857$$
$$x_{59} = 62.8318395642147$$
$$x_{60} = 4.18879020478639$$
$$x_{61} = 78.5398163397448$$
$$x_{62} = 15.707963267949$$
$$x_{63} = -4.18879020478639$$
$$x_{64} = -6.28314827212298$$
$$x_{65} = -81.6814264975776$$
$$x_{66} = -87.9646059618683$$
$$x_{67} = 75.3982472650144$$
$$x_{68} = -28.2743338823081$$
$$x_{69} = 90.0589894029074$$
$$x_{70} = -33.5103216382911$$
$$x_{71} = 43.9823032524319$$
$$x_{72} = -83.7758040957278$$
$$x_{73} = -35.6047167406843$$
$$x_{74} = 83.7758040957278$$
$$x_{75} = -48.1710873550435$$
$$x_{76} = 52.3598775598299$$
$$x_{77} = -10.471975511966$$