What is coming up due?

Sum and Difference of Cosine Section 5.3

Cosine of a Sum or Difference: cos (A + B) = cos A cos B – sin A sin B cos (A – B) = cos A cos B + sin A sin B cos (A  B) = cos A cos B sin A sin B 

Ex: Rewrite using the cosine sum/difference formula cos (90 – x)

Ex: Find the exact value a. cos 75

b. cos 7/12

c. cos 40 cos 50 – sin 40 sin 50

Cofunction Identities

Ex: Write in terms of the cofunction. tan 87 cos /12

c. csc (-1424) d. cot 176.9814

Ex: Use an identity to fill in the blank. _______ 33 = sin 57 cos 70 = 1/_______20

Ex: Find . a. tan  = cot (45º + 2) b. sec  = csc(/2 + 20º)

Ex: Rewrite as functions of . a. cos(0º –  ) b. cos (180º +  )

Ex: Find cos (s + t) and cos (s – t) a. cos s = -1/5 and sin t = 3/5 , s and t in QII

b. sin s = 3/5 and sin t = -12/13 , s in QI and t in QIII

Ex: True or False? a. cos 42º = cos (30 º+ 12º) b. cos 74º = cos 60º cos 14º + sin 60º sin 14º c. cos /3 = cos /12 cos /4 – sin /12 sin /4