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Maths A Level Edexcel - Area/Length/Perimeter of Sectors Questions Help

Hi can someone help me with this question please. I don't really know where to start with it I'm not sure if I'm supposed to use formula Area = 0.5 x radius squared x (angle) in part a and I dont know what to do for part b either. So can someone help me please. Thanks
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zlan
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Try the cosine rule cos x = ........
Original post by railgun267
Hi can someone help me with this question please. I don't really know where to start with it I'm not sure if I'm supposed to use formula Area = 0.5 x radius squared x (angle) in part a and I dont know what to do for part b either. So can someone help me please. Thanks


Hi! :smile:

For part (a), you need to find theta. In order to do so, you can use the cosine rule (however that's gonna be fairly cumbersome).

Might I suggest looking at it as an isosceles triangle. Split it up into two right angled triangles, and then you can solve it using basic trigonometry. You should find that sin (theta/2) = 0.75, and hence you can solve theta.

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Original post by railgun267
Hi can someone help me with this question please. I don't really know where to start with it I'm not sure if I'm supposed to use formula Area = 0.5 x radius squared x (angle) in part a and I dont know what to do for part b either. So can someone help me please. Thanks

For part (b), your answer to (a) would help.

From (a) you now know the value of theta.

Now in (b), you can equate the area (0.5 x radius squared x theta as you said) with 16pi
You can find out radius since you know theta.

Now once you know radius, perimeter = radius + radius + minor arc AB

hope that makes sense?

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