triangle

Neha · 2006-10-27 07:32:03

An equilateral triangle has an altitude of sqrt(3) and a perimeter of 9 .
what is the area of teh triangle?

of the area of triangle is = 1/2 bh

so what then.....:/

Toast · 2006-10-27 07:36:32

Since the triangle is equilateral, each side length will be the same, since there are three, you just divide 9 by 3 so the base is 3, and the height is sqrt(3).

Last edited by Toast (2006-10-27 07:38:02)

Neha · 2006-10-27 07:42:01

thank you so very much for you helping me out
i thought i hd to do something else in this problem...but i was wrong

mathsyperson · 2006-10-29 11:39:02

Incidentally, if you know the perimeter of the equilateral triangle then you don't need to know its height because that can be worked out anyway.

Alternatively, you could find the area using the semiperimeter rule, which is way cooler.

Toast · 2006-10-31 02:38:13

Please continue mathsyperson, what is the perimeter rule?

Is that the one where:

Where 'a' is the apothem and 'p' is the perimeter?
(btw is the apothem equal to half the height, cuz I tried and I got a different answer?)

mathsyperson · 2006-10-31 05:07:41

No, it's not that one. I think that's the one that lets you find the area of any regular polygon.

This one is specific to triangles, but they don't have to be regular.

Anyway, if s is the semiperimeter of the triangle and the sides are a, b and c (so s = (a+b+c)/2), then the area is:

For example, with an equilateral triangle of length 6, s would be (6+6+6)/2=9 and so A would be:

√(6*3*3*3) = √243 = 9√3

I like this rule because it is completely devoid of trigonometry.

Math Is Fun Forum

#1 2006-10-27 07:32:03

triangle

#2 2006-10-27 07:36:32

Re: triangle

#3 2006-10-27 07:42:01

Re: triangle

#4 2006-10-29 11:39:02

Re: triangle

#5 2006-10-31 02:38:13

Re: triangle

#6 2006-10-31 05:07:41

Re: triangle

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