Date: 04/11/2003 at 08:41:02 From: Lesley Subject: Area of Triangles Dear Dr. Math, How can I find the area of an isosceles triangle, an equilateral triangle, a scalene triangle, an obtuse-angle triangle and an acute- angle triangle without the height being given? Lesley
Date: 04/11/2003 at 12:03:43 From: Doctor Rick Subject: Re: Area of Triangles Hi, Lesley. You forgot to tell me what IS given! If you know the lengths of the three sides of a triangle, there is a formula called Heron's formula. I did not learn it when I was your age, as far as I can remember; it's more complicated than half the base times the height. First you calculate something called the semi- perimeter, s. As the name says, it's half the perimeter, that is, half the sum of the lengths of the sides: s = (a+b+c)/2 where a, b, c are the lengths of the sides Then you multiply this number by three other numbers - the semi- perimeter minus each of the three sides in turn - and take the square root of the result: A = sqrt(s(s-a)(s-b)(s-c)) That's the area of the triangle. Is this what you're looking for? - Doctor Rick, The Math Forum http://mathforum.org/dr.math/
Date: 04/11/2003 at 22:45:30 From: Lesley Subject: Thank you (Area of Triangles) Yup, that's the one. Thanks Dr. Math! Lesley
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