# QUICK Yo, I need me some help!!!!

• May 12th 2005, 07:31 PM
Cflow
30 60 90 and isosceles triangles
If a 30-60-90 degree right triangle and an isosolies right triangle have the same perimeter, which one will have the bigger area, and why?

I need to come up with the perimeters for both triangles as well, can ya'll help me?

Thank you bunches!
Love,
Carly
:confused:
• May 13th 2005, 01:08 AM
ticbol
30-60-90 triangle:
The leg opposite the 30-degree angle is the short leg.
The leg opposite the 60-degree angle is the long leg.

The hypotenuse is twice the short leg.
If x = short leg, then hypotenuse = 2x.
The longer leg then is x*sqrt(3).

Perimeter, P1,
= x +x*sqrt(3) +2x
= x +x(1.732) +2x
= x(4.732)

Isosceles right triangle:
The two legs are equal in length.
If y = one leg, then hypotenuse = y*sqrt(2).

Perimeter, P2,
= y +y +y*sqrt(2)
= y +y +y(1.4142)
= y(3.4142)

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"... have the same perimeter, which one will have the bigger area, and why?"

If P1 = P2, then,
x(4.732) = y(3.4142)
y = x(4.732)/(3.4142)
y = x(1.386) ...........****

Let us get the areas of both right triagles in terms of x.

Area of right triangle = (1/2)(base)(altitude) = (1/2)(leg)(other leg)

30-60-90:
A1 = (1/2)(x)(x*sqrt(3))
A1 = (0.866)(x^2)

isosceles:
A2 = (1/2)(y)(y)
A2 = (0.5)(y^2)
Substitute x(1.386) for y,
A2 = (0.5)(1.386x)^2
A2 = (0.96)(x^2)

So, since (A2 = 0.96x^2) is greater than (A1 = 0.866x^2), then,
Therefore, the isosceles right triangle has a bigger area. .....answer.

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"I need to come up with the perimeters for both triangles as well,..."

Since both perimeters are equal, then if you assign any value to x, (or y), you can get the perimeters.

If x = 1,
P1 = P2 = x(4.732) = 1(4.732) = 4.732

If x = 2,
P1 = P2 = x(4.732) = 2(4.732) = 9.464

If x = 8,
P1 = P2 = x(4.732) = 8(4.732) = 37.856

Based upon the given information, there is no unique value for the perimeter.