Answer:
D
Step-by-step explanation:
Answer:
78.0 ft
Step-by-step explanation:
pythagoras theorem =
a² + b² = c²
a² + 36² = 85.9²
a² + 1296 = 7378.81
a² = 7378.81 - 1296
a² = 6082.81
a = √6082.81
a = 77.992....
so, a (rounded) = 78 ft :)
Answer:
Identity (a) can be re-written as

which we already proven in another question, while for idenity (b)

step A is simply expressing each function in terms of sine and cosine.
step B is adding the terms on the LHS while multiplying the one on RHS.
step C is replacing the term on the numerator with the equivalent from the pithagorean identity 
Well if you tell me the distance of abcd from the speaker I could help u