7 Aug 2013

Irish MO 1988 P1 Q4: Upper Secondary Mathematics Competition Question


A mathematical moron is given the values b, c, A for a triangle ABC and is required to find the value of a. He does this by using the cosine rule

a2 = b2 + c2 - 2bc.cosA

and misapplying the law of logarithms to this to get

log(a2) = log(b2) + log(c2) - log(2bc.cosA).

He proceeds to evaluate the right-hand side correctly, takes the anti-logarithms and gets the correct answer. What can be said about the triangle ABC?

[ Irish MO 1988 Paper 1 Question 4]

The wording is genuine :-)



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