Rational Sine and CosinePro Problems > Math > Logic > Proofs
Rational Sine and Cosine
There are infinitely many angles θ between 0º and 90º for which both sin θ and cos θ are rational numbers. Prove this statement.
Hint: Here are some examples:
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Prove that all perfect squares are either a multiple of 4, or one more than a multiple of 4.
Prove that there is no two digit number which is equal to the product of its digits.
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