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An isosceles triangle with perimeter 12 is constructed.

  1. Find the largest possible area of the triangle.

  2. Explain the significance of your solution.


It would be convenient to let the two equal sides have length a, and then the base of the triangle have length 2b for some b, as below:


Because the perimeter is 12, we have

2a+2b=12

Also, by Pythagoras, we have

a2=b2+h2

If you want to maximise

A=12bh

it would be sufficient to maximise A2. This makes the problem much easier.


Get A2 in terms of b only, and solve

d(A2)db=0

to find the turning point.


As a fully simplified surd, the area is

pq

Give the value of qp.