SOLUTION: A square and an equilateral triangle have equal perimeters. The area of the triangle is 163 square centimeters. How long, in centimeters, is a diagonal of the square? Express your

Algebra ->  Formulas -> SOLUTION: A square and an equilateral triangle have equal perimeters. The area of the triangle is 163 square centimeters. How long, in centimeters, is a diagonal of the square? Express your       Log On


   



Question 986224: A square and an equilateral triangle have equal perimeters. The area of the triangle is 163 square centimeters. How long, in centimeters, is a diagonal of the square? Express your answer in simplest radical form.
Thank you

Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Triangle, side length s.
Altitude cuts triangle into two special 30 60 90 triangles.
A, the area of The equilateral triangle,
A/2, area of one of the special triangles.
a, altitude of the triangle.
a%5E2%2B%28s%2F2%29%5E2=s%5E2
a%5E2=s%5E2-%28s%2F2%29%5E2
a%5E2=s%5E2-%281%2F4%29s%5E2
a%5E2=%283%2F4%29s%5E2
a=%28s%2F2%29sqrt%283%29
A=2%28%281%2F2%29%28a%2F2%29%28s%2F2%29sqrt%283%29%29, one-half base times height, twice
A=2a%2As%2Asqrt%283%29%2F%282%2A2%2A2%29
A=a%2As%2Asqrt%283%29%2F%282%2A2%29
substitute for a,
A=%28%28s%2F2%29sqrt%283%29%29%2As%2Asqrt%283%29%2F%282%2A2%29
A=%283%2As%5E2%29%2F8
Solve for s
s%5E2=A%2A8%2F3
s=2sqrt%282A%2F3%29


The SQUARE
Let x be the edge of square shape.
4x=3s
because perimeter of square is given as equal to perimeter of the equilateral triangle.
x=%283%2F4%29s
The diagonal of the square is d.
x%5E2%2Bx%5E2=d%5E2
d=sqrt%282x%5E2%29
d=x%2Asqrt%282%29
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Substitute for x to get better formula for d.
d=%283%2F4%29s%2Asqrt%282%29
Substitute for s to get yet a better formula for d.
d=%283%2F4%29%2A%282sqrt%282A%2F3%29%29%2Asqrt%282%29
d=%283%2F2%29sqrt%282%29sqrt%282A%2F3%29
d=%283%2F2%29sqrt%282%29sqrt%282%29sqrt%28A%2F3%29
d=3%2Asqrt%28A%2F3%29
Rationalize the expression, the denominator...
d=3%2Asqrt%283%29sqrt%28A%29%2F3
and remember, given A=163....
highlight%28d=sqrt%283%29sqrt%28163%29%29