Solve the following equality : cos2v=cos40

Take the inverse cosine of both sides.

... arccos(cos(2v)) = arccos(cos(40°))

... 2v = ±40° + k·360° . . . . . for k = any integer

... v = ±20° + k·180° . . . . . . for k = any integer

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.