SOLUTION: find the largest area possible for a right triangle whose hypotenuse is 5 inches long

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Question 958882: find the largest area possible for a right triangle whose hypotenuse is 5 inches long
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!


Area%22%22=%22%22expr%281%2F2%29%28base%29%28height%29

Let the area be y.

y%22%22=%22%22expr%281%2F2%29x%2Asqrt%2825-x%5E2%29













Set y' equal to 0 to find relative extrema:







Square both sides:







Multiply both sides by the denominator on the right



Take positive square roots of both sides:

matrix%282%2C3%2C%22%22%2C%22%22%2C%22%22%2C%0D%0A%0D%0A25-x%5E2%2C%22%22=%22%22%2Cx%5E2%29


25-x%5E2%22%22=%22%22x%5E2

25%22%22=%22%222x%5E2

25%2F2%22%22=%22%22x%5E2

Take positive square roots of both sides:

sqrt%2825%2F2%29%22%22=%22%22x

5%2Fsqrt%282%29%22%22=%22%22x

Rationalize the denominator:

5sqrt%282%29%2F2%22%22=%22%22x

So the base is 5sqrt%282%29%2F2

We find the height but substituting in

height = sqrt%2825-x%5E2%29

height = sqrt%2825-%285sqrt%282%29%2F2%29%5E2%29


height = sqrt%2825-25%2A2%2F4%29

height = sqrt%2825-25%2F2%29

height = sqrt%2825%2F2%29

height = 5%2Fsqrt%282%29

height = 5sqrt%282%29%2F2

So the dimensions of the right triangle with maximum area has

base and height both equal to  5sqrt%282%29%2F2

which is an isosceles right triangle.

Its area is found by substituting 5sqrt%282%29%2F2 into:

y%22%22=%22%22expr%281%2F2%29x%2Asqrt%2825-x%5E2%29

y%22%22=%22%22expr%281%2F2%29%285sqrt%282%29%2F2%29%2Asqrt%2825-%285sqrt%282%29%2F2%29%5E2%29

y%22%22=%22%22%285sqrt%282%29%2F4%29%2Asqrt%2825-25%2A2%2F4%29

y%22%22=%22%22%285sqrt%282%29%2F4%29%2Asqrt%2825-25%2F2%29

y%22%22=%22%22%285sqrt%282%29%2F4%29%2Asqrt%2825%2F2%29

y%22%22=%22%22%285sqrt%282%29%2F4%29%2A%285%2Fsqrt%282%29%29

y%22%22=%22%22%285cross%28sqrt%282%29%29%2F4%29%2A%285%2Fcross%28sqrt%282%29%29%29

y%22%22=%22%22%285%2F4%29%2A5

y%22%22=%22%2225%2F4

The maximum area is 25%2F4 or 6%261%2F4 square inches.

The triangle with maximum area looks like this:



Edwin