Answer with Step-by-step explanation:
We are given that A and B are two countable sets
We have to show that if A and B are countable then 
is countable.
Countable means finite set or countably infinite.
Case 1: If A and B are two finite sets
Suppose A={1} and B={2}
={1,2}=Finite=Countable
Hence, is countable.
Case 2: If A finite and B is countably infinite
Suppose, A={1,2,3}
B=N={1,2,3,...}
Then, ={1,2,3,....}=N
Hence, is countable.
Case 3:If A is countably infinite and B is finite set.
Suppose , A=Z={..,-2,-1,0,1,2,....}
B={-2,-3}
=Z=Countable
Hence, countable.
Case 4:If A and B are both countably infinite sets.
Suppose A=N and B=Z
Then,=
=Z
Hence, is countable.
Therefore, if A and B are countable sets, then is also countable.
Subtract the sum of the known sides from the perimeter to find the length of the missing side.
There are 30.48 centimeters in a foot
Answer: 1/2, 1/2, 1/4
Step-by-step explanation:
To find the fraction that the hour hand turns of a clockwise revolution, we have to find how long it is going then divide by 12
Ex. a) 11 - 5 = 6, 6/12 = 1/2 so the hour hand turns by 1/2 of a clockwise revolution
b) 8 - 2 = 6, 6/12 = 1/2 so the hour hand turns by 1/2 of a clockwise revolution
c) For this, we have to convert 1 into 13 as 1 - 10 is a negative number
13 - 10 = 3, 3/12 = 1/4 so the hour hand turns by 1/4 of a clockwise revolution
