Prove that the area of the equilateral triangle drawn on the hypotenuse of a right angled triangle is equal to the sum of the areas of the equilateral triangles drawn on the other two sides of the triangle.
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Given: A right triangle ABC.
Let AB = a, BC = b, AC = C and $\text{B}=\angle\text{90}^\circ$
Equilateral triangle with sides AB = a, BC = b and AC = C are drawn respectively.
To prove: Area of equilateral triangle with side hypotenuse (c) is equal to the area of equilateral triangle with side a and b.
$\text{or}\frac{\sqrt{3}}{4}\text{c}^2=\frac{\sqrt{3}}{4}\text{a}^2=\frac{\sqrt{3}}{4}\text{b}^2$
Proof: In $\triangle\text{ABC},$
$\angle\text{ABC}=90^\circ$ [Given]
$\therefore\text{AC}^2=\text{AB}^2+\text{BC}^2$ [by Pythagoras theorem]
$\Rightarrow\text{c}^2=\text{a}^2+\text{b}^2$
$\Rightarrow\frac{\sqrt{3}}{4}\text{c}^2=\frac{\sqrt{3}}{4}\text{a}^2=\frac{\sqrt{3}}{4}\text{b}^2$
[Multiplying by $\frac{\sqrt{3}}{4}$ to both sides]
(Area of equilateral $\triangle$ with side c) = (Area of equilateral $\triangle$ with side a) + (Area of equilateral $\triangle$ with side b)
Hence, the area of equilateral $\triangle$ With hypotenuse is equal to the sum Hence, proved.
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