Suppose sina = 12/13 with 90º≤a≤180º. suppose also that sinb = -7/25 with -90º≤b≤0º. find cos(a + b).

Bear in mind that, the angle A is in the range of the II quadrant, where "y" is positive and "x" is negative.





now for angle B, bear in mind it's on the IV quadrant, and "y" is negative there whilst "x" is positive.

another thing, the sine is negative, but sine is opp/hyp, now, the hypotenuse is just a radius unit, and therefore never negative, so the negative in the fraction must be the numerator, thus is -7.



so, now, we have all sides, so lets' add cos(A + B) then

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.