Answer:
12
Step-by-step explanation:
x = 2n
2n + 2n + 2 + 2n + 4 + 2n + 6 + 2n + 8 = 80
10n = 60
n = 6
x = 12
12 + 14 + 16 + 18 + 20 = 80
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 
Answer:
<3<6<4<5 are alternate interior
<1<8<2<7 are alternate exterior
<2<3<5<8 are vertical angles
<1<5<2<6 are corresponding angles
Step-by-step explanation:
Have a look at the attached image.