1. ## perimeter very easy

There's a square drawn here and it's diagonal is shown as being 6sqrt3 cm long
and i have to find the perimeter..how do i do this?

2. Originally Posted by kri999
There's a square drawn here and it's diagonal is shown as being 6sqrt3 cm long
and i have to find the perimeter..how do i do this?
let the side length be $\displaystyle x$.

then by Pythagoras' theorem, $\displaystyle x^2 + x^2 = (6 \sqrt{3})^2 = 108$

solve for $\displaystyle x$. then the perimeter is given by $\displaystyle 4x$

3. oh yes sorry i forgot to mention that i have to use the rule about 45 45 90 triangles with this problem

4. Originally Posted by kri999
oh yes sorry i forgot to mention that i have to use the rule about 45 45 90 triangles with this problem
why? that would only make your life harder. then you'd have to use sine or cosine or tangent or something

if you insist, you could do $\displaystyle \sin 45 = \frac x{6 \sqrt{3}}$ and solve for x from that

5. Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

That's all i don't understand

6. Originally Posted by kri999
Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

That's all i don't understand
Well $\displaystyle x = \frac{6 \sqrt{3}}{\sqrt{2}} = \frac{6 \sqrt{3} \sqrt{2}}{\sqrt{2} \sqrt{2}} = \frac{6 \sqrt{6}}{2} = 3 \sqrt{6}$.

And the perimeter is equal to 4x.

Therefore ......

7. Originally Posted by kri999
Yeah sorry the whole chapter is on sines and cosines and special triangles, so they insist on making life harder. haha..they gaave the answer as 12 sqrt 6

That's all i don't understand
it would be good if you told us your difficulty. if you have trouble setting up the sine, cosine and tangent trig ratios, say so, and we can address it. if your problem was the algebra, then Mr. Fantastic already addressed that. do you understand the problem now? or is there something else?