word problem- fun one... trust me....

renegade05

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Sep 10, 2010
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I think i got this one, i just wanted to confirm that i didnt screw something up.

The tirangle shown is isosceles with base x.
isosceles-triangle.png


Find the function, P, that gives the perimeter of the triangle as a function of the base, x, if its area is 10m².

So...this is what i did.
variables:

\(\displaystyle x = base\)

\(\displaystyle h = height\)

\(\displaystyle a = \frac{1}{2} of base = \frac{x}{2}\)

\(\displaystyle c = hypotonus\)

work:

\(\displaystyle \frac{xh}{2} = 10m^2\)

\(\displaystyle h = \frac{20m^2}{x}\)

then:

\(\displaystyle a^2+h^2=c^2\)

\(\displaystyle (\frac{x}{2})^2+(\frac{20}{x})^2=c^2\)

\(\displaystyle \sqrt{(\frac{x}{2})^2+(\frac{20}{x})^2}=c\)

ANSWER:

\(\displaystyle P(x)=x+2\sqrt{(\frac{x}{2})^2+(\frac{20}{x})^2}\)
 


Your reasoning seems sound.

Can you simplify the expression, in your final result ?

I get:

\(\displaystyle P(x) \;=\; x \;+\; \frac{1}{x} \cdot \sqrt{x^4 + 1600}\)

 
mmm4444bot said:


Your reasoning seems sound.

Can you simplify the expression, in your final result ?

I get:

\(\displaystyle P(x) \;=\; x \;+\; \frac{1}{x} \cdot \sqrt{x^4 + 1600}\)


simplified is always good. I like your answer better. thanks for the confirmation and help.
 
renegade05 said:
I like your answer better.

I hope that it's correct.

You could verify function P by picking one or two values for x, and then determining the perimeter of those two triangles both by hand and by function. Each method should produce the same perimeter, yes?

 
mmm4444bot said:
renegade05 said:
I like your answer better.

I hope that it's correct.

You could verify function P by picking one or two values for x, and then determining the perimeter of those two triangles both by hand and by function. Each method should produce the same perimeter, yes?


yup.

I verified it.

Oh math .... you're like a beautiful women...always right.
 
renegade05 said:
I verified it.

Oh math .... you're like a beautiful women...always right.

Who said that .... Shelly .... Keats .... Byron .... Swinburn ..... certainly not Khan.....
 
Subhotosh Khan said:
renegade05 said:
I verified it.

Oh math .... you're like a beautiful women...always right.

Who said that .... Shelly .... Keats .... Byron .... Swinburn ..... certainly not Khan.....

my math teacher is always talking about how beautiful math is. I just added to what she is always saying.
 
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