This idea was hard to convey to the students. One thing students must understand is the meaning of the word “truth” in mathematics. Truth means consistency. We contrast this with truth in science, which means the phenomena can be observed or experimentally verified. It would help if the teacher would give an example where indirect proof is necessary.

 

A discussion can be found at

 

http://regentsprep.org/Regents/mathb/1e/indirectlesson.htm.

 

Assume what you need to prove is false, and then show that something contradictory happens.