## anonymous 4 years ago If the altitude of an equilateral triangle is 12cm, find its area.. According to the answer sheet, answer is 83.1cm^2

1. anonymous

yeah looks good to me

2. anonymous

Erm.. How do you solve it?

3. anonymous

|dw:1328411891637:dw|

4. anonymous

you need the base. now since this is an equilateral triangle, all sides are equal. and that is what we are looking for, one of the sides. lets call is it x|dw:1328412007974:dw|

5. anonymous

ok..

6. anonymous

then pythagoras tells you that $(\frac{1}{2}x)^2+12^2=x^2$ $12^2=x^2-\frac{1}{4}x^2$ $144=\frac{3}{4}x^2$ $x^2=144\times \frac{4}{3}=192$ $x=\sqrt{192}=6\sqrt{3}$

7. anonymous

|dw:1328412341534:dw|

8. anonymous

|dw:1328423226163:dw|

9. anonymous

|dw:1328423349746:dw|

10. anonymous

|dw:1328423488080:dw|

11. anonymous

Thank you :)

12. anonymous

yw

13. anonymous

? yw?

14. anonymous

15. anonymous

Oh I didn't know :P We usually use np (no problem) in Sg

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