# Solution: 2013-03 Hyperbolic cosine

Let $$t$$ be a positive real number and $$m$$ be a positive integer. Show that if both $$\cosh \, mt$$ and $$\cosh \, (m+1)t$$ are rational then $$\cosh \, t$$ is also rational.

The best solution was submitted by 홍혁표, 13학번. Congratulations!

Other solutions were submitted by 라준현(08학번, +3), 서기원(09학번, +3), 김호진(09학번, +3), 김범수(10학번, +3), 박지민(12학번, +3), 김정민(12학번, +2), 양지훈(10학번, +2), 황성호(13학번, +2). Thank you for your participation.

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