answer:
[tex]{ \tt{ \cos(100x) + \frac{4}{3} = 0}} \\ { \tt{ \cos(100x) = - \frac{4}{3} }} \\ { \tt{100x = { \cos }^{ - 1} ( - \frac{4}{3} )}} \\ { \tt{invalid \: answer}}[/tex]
