Finding the area of the triangle

Question

There is a point inside a equilateral triangle which is at a distance 1,2 and 3 from the sides then what is the area of the triangle? Please help me.

An application of Viviani Theorem, perhaps. – Sawarnik Dec 29 '13 at 05:13 — Sawarnik, Dec 29 '13 at 05:13

score 3 · Answer 1 · answered Oct 12 '11 at 16:24

3

Hint: The height of the equilateral triangle must be the sum of the distances between an internal point and the sides.

answered Oct 12 '11 at 16:24

hmakholm left over Monica

286,031

score 1 · Answer 2 · answered Oct 12 '11 at 16:14

1

Suppose that the triangle ABC has sidelength $a$ and the point in the interior is P. Now calculate the areas of ABP, BCP and CAP (you know their base and height !) and compare it with the formula for the area of an equilateral triangle.

This gives you $a$, so you can calculate the area, too.

answered Oct 12 '11 at 16:14

Phira

20,860

This is the obvious way to do it. Some other ways are more complicated. – Michael Hardy Oct 12 '11 at 18:44

score 0 · Answer 3 · answered Oct 12 '11 at 16:34

Let's denote :

$AE=a_1 , BE=a_2 , BG=a_3 . GC=a_4 , FC=a_5 , AF=a_6$ ,$ED=1 ,DF=2 ,DG=3$(see picture bellow)..then:

$A=\frac{a_1}{2}+\frac{a_2}{2}+\frac{3a_3}{2}+\frac{3a_4}{2}+\frac{2a_5}{2}+\frac{2a_6}{2}=\frac{a}{2}+\frac{3a}{2}+a=3a$

You may calculate $a$ from equality $$3a=\frac{a^2\sqrt{3}}{4}$$

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Finding the area of the triangle

3 Answers3