Harmonic ProofPro Problems > Math > Logic > Proofs > Indirect Proofs
Create an indirect proof for the following statement: The harmonic mean of any two positive numbers lies inclusively between the two numbers.
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Hint: An irrational number is a number which cannot be written as the quotient of two relatively prime integers.
Use an indirect proof to show that there are infinitely many prime numbers.
For every positive rational number x, there exists a smaller positive rational number y. Prove this statement by indirect proof.
Prove by contradiction: for any integers x, y, and z with z > 1, x2 - yz2 ≠ z.
Hint: This is a more generalized version of the problem found here: X Squared Proof
Let a and b be positive integers, with b not a perfect square. Show that the following expression is irrational, using an indirect proof.
Hint: Remember that an irrational number is a number which cannot be written as the quotient of two integers.
Prove by indirect method that if x and y are integers, then x2 - 9y ≠ 3.
Show that if θ is between 0º and 90º inclusive, then sin θ + cos θ ≥ 1. Use an indirect proof.
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