An indirect proof has been successful if you reach a contradiction of a known fact. a. true b. false c. cannot tell

True

Step-by-step explanation:

First we must understand the difference between direct and indirect proof

A direct proof assumes that the hypothesis of a conjecture is true, and then uses a logical well defined arguments  to prove that the conclusion of the conjecture is true.

An indirect proof assumes that it is not true and hence relies  on a contradiction to prove , and then running into a contradiction proving that the conjecture must be true.

Thus we assume a contradiction and proceed then we get a wrong conclusion stating that our assumption is false.

Thus a) True.

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step-by-step explanation:

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