A
rational number is any number that can be written as the
ratio between two other numbers i.e. in the form

Part A:
An easy choice that makes sense is 7.8, right in the middle. To prove that it's rational we need to write it as a ratio. In this case we have

Part B:
We need a number that can't be written as a ratio (because it neither terminates nor repeats). Some common ones are

,

,

and

so it makes sense to try and use those to build our number. In this case

works nicely.
Answer:
FIRST ONE
Step-by-step explanation:
NO NUMBER REPEATS ITSELF
Hello,
cos 160°=-q
cos 20°=-cos 160°=q
sin 20°=√(1-q²)=sin 160°
tan -20°=tan 160=√(1-q²)/-q
cos 70°=sin 20°=√(1-q²)
Width: W
length: L = 5W
Use the Pyth. Theorem to find the length of the diagonal:
|D| = sqrt(W^2 + [5W]^2) = sqrt(W^2 + 25W^2) = sqrt(26W^2), or
Wsqrt(26) (ans.)