Just a guess but 75 degrees?
Answer:
bahw1jnajw21q894j281833837747474748281813
Hello,
N is closed for an opération(µ) means that
a,b ∈ N : a µ b ∈N (i suppose so)
Answer (1) ex 2/3 ∉ N
Answer (4) ex 2-3 ∉ N
∀ a,b ∈ N: a+b ∈N is true ; not a answer.
∀ a,b ∈ N: a*b ∈N is true ; not a answer.
Cos(x) = 50/100
part a) x= 60°
<span>part b) height is 86.60254040</span>