There are three elements in that set.
Answer:

Step-by-step explanation:
<u>Use identities to set the equation up as a quadratic</u>

<u>Make the substitution u=cos(x) and solve the quadratic</u>
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Hence, 
Answer:
Oaktown had 9 times more inches of rain than Pine City did.
Step-by-step explanation:
63 divided by 7 = 9.
Very simple problem. Glad to help.
I think it is the associative property of Addition