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CBSE Class 9 Answered

sir i want to know how to derive a formulae
Asked by shreyansh panwar | 24 Aug, 2010, 09:26: PM
answered-by-expert Expert Answer
This is the formula for area of an equilateral triangle with side 'a'.
The area of a triangle is half base x height.
In an equilateral triangle, we draw a perpendicular to the base, whih is a median and height of the triangle. Each angle is 60 degrees.
So using Pythagoras theorem, h2 +(a/2)2 =a2
Hence             h2= a2 - (a/2)2 = 3a2/4 
 
So h =root3a/2
Area of the triangle = (1/2) a h = (1/2)a (root 3 a/2)=(root3) a2/4
Answered by | 25 Aug, 2010, 09:51: AM

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