The cone is made from this sector. Find correct to 3 significant figures.

[EddyBenzen122]

I'm having trouble figuring out part c and d. For part c, I'd need both the radius and the angle to find the arc length but the angle is unknown. The value of r in part b is the same as the slant length in part a which is 11.7cm(s = √10^2 + √6^2 = 11.7cm )So what could be another way to find the arc length if the angle is missing? The photo above is the question from my IB Math Textbook.

 

[Otis]

what could be another way to find the arc length

Hi Eddy. Here's a question for you to ponder. What forms the cone's circular base?

the slant length … s = √10^2 + √6^2 = 11.7

I think you've used the Pythagorean Theorem to find s, but the radical expression you've typed above is not correct. Can you see why?

11.7 is correct.

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[Otis]

s = √10^2 + √6^2

To clarify for other readers, here's a correct way to type that radical expression.

s = √(10^2 + 6^2)

s = √136

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