The intersection of two sets, written

is the set that contains all elements in BOTH of the original sets.
In this case:

Unless you are told somewhere else what a and b are equal to, none of the given choices is correct.
Answer:
C AAA is not an accepted triangle congruence criterion
Step-by-step explanation:
AAA can be used to show similarity, but not congruence. At least one side must be involved in any triangle congruence claim.
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The student could have made use of the fact that opposite sides are the same length, and used AAS or ASA to show congruence.
Answer:
I got the answer of 21.99115. Do I need to round too? If so, look up a rounding calculator and you can put in that decimal number and round to what the question says to round to.
I hope this helps!