Sin(A + B) = sinAcosB + cosAsinB
cos(A + B) = cosAcosB - sinAsinB
If sinA = ⅗ and sinB = 5/13 where both angles A & B are in quadrant II. Find sin(A + B).
sinA = ⅗ & cosA = -⅘ and sinB = 5/13 & cosB = -12/13
sin(A + B) = (⅗)(-12/13) + (-⅘)(5/13) = (-36/65) + (-20/65) = -56/65

USING THIS INFORMATION FIND cos(A+B)

Exercise: counting committees 0.0/2.0 puntos (calificable) we start with a pool of n people. a chaired committee consists of k≥1 members, out of whom one member is designated as the chairperson. the expression k(nk) can be interpreted as the number of possible chaired committees with k members. this is because we have (nk) choices for the k members, and once the members are chosen, there are then k choices for the chairperson. thus, c=∑k=1nk(nk) is the total number of possible chaired committees of any size. find the value of c (as a function of n ) by thinking about a different way of forming a chaired committee: first choose the chairperson, then choose the other members of the committee. the answer is of the form c=(α+nβ)2γn+δ. what are the values of α , β , γ , and δ ?