Answer:
[tex]A=\frac{\sqrt{3}}{4}a^2[/tex]
Step-by-step explanation:
Since an equilateral has all of the sides equal, we can find the height of triangle using: [tex]a^2+b^2=c^2[/tex]. I attached a diagram which should explain how I got the dimensions of the three sides. Using the information from the diagram we get the equation:
[tex]h^2+(\frac{a}{2})^2=a^2[/tex]
Subtract a^2 from both sides
[tex]h^2=a^2-(\frac{a}{2})^2[/tex]
Take the square root of both sides
[tex]h = \sqrt{a^2-(\frac{a}{2})^2}[/tex]
If you know the area of a triangle, it's: [tex]\frac{1}{2}bh[/tex]. In this case the base=a, and the height is what we defined above. Using this we get:
[tex]A = \frac{a}{2}*\sqrt{a^2-(\frac{a}{2})^2}[/tex]
We can distribute the exponent over the division to get:
[tex]A = \frac{a}{2}*\sqrt{a^2-(\frac{a^2}{4})[/tex]
Now we can rewrite a^2 as 4a^2/4
[tex]A = \frac{a}{2}*\sqrt{\frac{4a^2}{4}-(\frac{a^2}{4})[/tex]
Now add the two fractions:
[tex]A = \frac{a}{2}*\sqrt{\frac{3a^2}{4}[/tex]
We can distribute the square root the division just like how we distributed the exponent 2, since the square root can be expressed as an exponent (1/2)
[tex]A = \frac{a}{2}*\frac{\sqrt{3a^2}}{\sqrt{4}}[/tex]
There's a radical identity that states: [tex]\sqrt[n]{a} * \sqrt[n]{b} = \sqrt[n]{a*b}[/tex]. We can use this to rewrite one radical as multiple radicals to simplify it:
[tex]A = \frac{a}{2}*\frac{\sqrt{a^2}*\sqrt{3}}{2}[/tex]
Simplify:
[tex]A = \frac{a}{2}*\frac{a*\sqrt{3}}{2}[/tex]
Now multiply the two fractions
[tex]A = \frac{a^2*\sqrt{3}}{4}[/tex]
This is the formula for the area of an equilateral triangle, but it is also often written as:
[tex]A=\frac{\sqrt{3}}{4}a^2[/tex]
