## stupidinmath Group Title --- 6 months ago 6 months ago

1. stupidinmath Group Title

I'm quite confused. i dont know now T.T arc length: l = 2(theta)(r)(theta/360) l = 2(90)(5)(90/360) l=225 225x4 = 900 perimeter is 900cm

2. ganeshie8 Group Title

arc length : $$\large l = 2 (\theta)r \frac{\pi}{360}$$ now try

3. stupidinmath Group Title

oh, wrong formula. ok let me solve it:)

4. lncognlto Group Title

This is just a thought, but wouldn't the perimeter of the shaded region be equal to the circumference of a circle with a radius of 5 cm?

5. ganeshie8 Group Title

Or, you can see that there are four quarter arcs of radius 5 which give u 1 complete perimeter of circle of radius 5

6. ganeshie8 Group Title

^^ Yes :)

7. stupidinmath Group Title

my arc length is 7.85 so.. my perimeter of the shaded region is 31.42 approximately. is that right?

8. ganeshie8 Group Title

$$\large \color{red}{\checkmark}$$ next try if you get lncognlto's suggestion...

9. stupidinmath Group Title

ah, yes, thanks. and yup, what he said was right:) I just need a complete solution though:) thanks guys

10. ganeshie8 Group Title

both methods are considered complete solutions :) u wlc :) however ur teacher wud get more impressed if u do the lncognlto's method...

11. stupidinmath Group Title

oh, haha, alright, will do that :)

12. ganeshie8 Group Title

good :D

13. stupidinmath Group Title

@ganeshie8 , if this is the problem.. would the formula still be 2(theta)(r)(pi/360) or it should be 2(theta)(2)(pi/180)?

14. ganeshie8 Group Title

Alright, here is the original formula :- arc length $$l = r\theta$$ $$\theta$$ is in radians

15. ganeshie8 Group Title

to convert given $$\theta$$ degrees into $$\theta$$ radians, u multiply $$\frac{2\pi}{360}$$ which is same as multiplying $$\frac{\pi}{180}$$ :- arc length $$l = r \theta \frac{2\pi}{360}$$ $$\theta$$ is in degrees now

16. ganeshie8 Group Title

for the triangle, did they give u any dimensions ?

17. stupidinmath Group Title

thank you so much. yep, ill post my solution later for checking:)

18. lncognlto Group Title

May I give another thought? xD

19. stupidinmath Group Title

sure:)

20. ganeshie8 Group Title

sure :)

21. lncognlto Group Title

If this triangle is equilateral, then the angles of each of the sectors is going to be 60 degrees. Thus three sectors together make 180 degrees, or half a circle. So the perimeter of the shaded region would then be equal to half the circumference of a circle with the radius equaling half the length of a side of the triangle.

22. stupidinmath Group Title

oh, that's right. smart one. Hahaha. will remember that:)

23. ganeshie8 Group Title

60 + 60 + 60 and 180 which one save u time ha ? I'm sure ur teacher wants u do this exactly as lcognlto suggests !

24. stupidinmath Group Title

i believe so too:)