Answer:
Step-by-step explanation:
Cos(A + B) = Cos(A)*Cos(B) - Sin(A)*Sin(B)
Find The Hypotenuse of A
Tan(A) = Opposite / Adjacent
Tan(A) = 15/8
Opposite = 15
Adjacent = 8
Hypotenuse = c
c^2 = opposite^2 + Adjacent^2
c^2 = 15^2 + 8^2
c^2 = 225 + 64
c^2 = 289
sqrt(c^2) = sqrt(289)
c = 17
Find the opposite of B
Adjacent = 12
Hypotenuse = 37
Opposite = b
adjacent^2 + opposite^2 = hypotenuse^2
12^2 + b^2 = 37^2
144 + b^2 = 1369
b^2 = 1369 - 144
b^2 = 1335
b = 35
Definitions
Sin(A) = Opposite / hypotenuse = 15/17
Sin(B) = opposite / hypotenuse = 35/37
Cos(A) = 8/17
Cos(B) = 12/37
Answer
Cos(A + B) = Cos(A)*Cos(B) - Sin(A)*Sin(B)
Cos(A + B) = 8/17 * 12/37 - 15/17*35/37
Cos(A + B) = 96/629 - 525/629
Cos(A + B) = -429/629
