Natural number - 5
Irrational number - π
The answer is D. It is an integer but not a whole number. Whole numbers start with 0 and the continues positively.... 0 , 1, 2, 3, 4, 5,...
Greatest Common Factor: 12-1/3 = -4/12, 7/4 = 21/12-4/12 + 21/12 = 17/12
Answer in simplest form: 17/12
Answer: see proof below
<u>Step-by-step explanation:</u>
Use the Double Angle Identity: cos 2A = 2cos²A - 1
Use the Difference Identity: cos (A - B) = cosA · cosB + sinA · sinB
Use the Unit Circle to evaluate: cos (π/2) = 0 & sin (π/2) = 1
<u>Proof LHS → RHS</u>

LHS = RHS: sin A = sin A 
First piece is x
second piece is y. y=4x
third piece is z. z=3y=12x
x+y+z=680
x+4x+12x=680
17x=680. x=40cm y=160cm. z=480cm