Is the Pythagoras theorem true for right triangle on a sphere? ______
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The recurring decimal 0.124124124… can be written in fraction as______ .
If ______ , then a is the quotient of c and b (b≠0).
If ______ , we call a is the difference between c and b.
(n+m)+k=n+(m+k)is called ______ of addition
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