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Need help with this DIFFICULT QUESTION :/

is this A Level
Reply 2
Avatar for B_9710
B_9710
18
Polar integration will help. But I'm assuming this is AS?
Actually looking at it polar would be of no use really.
(edited 7 years ago)
Reply 3
Avatar for B_9710
B_9710
18
Notice that it says OB and OC are arcs of circles.
AOB = Equilateral Triangle.

The angle = pie/3 as a result.

Find the area of the semi circle to the left.

Use pie/3 as an angle to find both sectors.

Add these up, then take away from the area of the whole circle.
Reply 5
Avatar for Adorable98
Adorable98
OP
15
Original post by Bigbosshead
AOB = Equilateral Triangle.

The angle = pie/3 as a result.

Find the area of the semi circle to the left.

Use pie/3 as an angle to find both sectors.

Add these up, then take away from the area of the whole circle.


But how do you know AOB is Equilateral Triangle? :s-smilie:
Reply 6
Avatar for Adorable98
Adorable98
OP
15
Solomon paper L
I was thinking the same until i realised that:

AO = OB

AB = AO

therefore AO = AB = OB
Reply 8
Avatar for Notnek
Notnek
21
Original post by Adorable98
But how do you know AOB is Equilateral Triangle? :s-smilie:

You are told that arc OB is an arc of a circle with radius r and centre A.

So AO and AB must be equal since they have to be radii of that circle with centre A.

And AO = OB since they're both radii of the main circle.

So AO = AB = OB.
Reply 9
Avatar for SM45367
SM45367
10
Same question was posted 3 days ago:
http://www.thestudentroom.co.uk/showthread.php?p=65004729&highlight=

should be useful^
Original post by B_9710
Polar integration will help. But I'm assuming this is AS?
Actually looking at it polar would be of no use really.

I mean, you could...

Spoiler



But this is slightly more involved than simply working out the segment directly (since, in this case, the arc is all circular and nice) and therefore excessive.
(edited 7 years ago)
Original post by notnek
You are told that arc OB is an arc of a circle with radius r and centre A.

So AO and AB must be equal since they have to be radii of that circle with centre A.

And AO = OB since they're both radii of the main circle.

So AO = AB = OB.


Original post by Bigbosshead
I was thinking the same until i realised that:

AO = OB

AB = AO

therefore AO = AB = OB


Original post by Bigbosshead
AOB = Equilateral Triangle.

The angle = pie/3 as a result.

Find the area of the semi circle to the left.

Use pie/3 as an angle to find both sectors.

Add these up, then take away from the area of the whole circle.


Original post by B_9710
Notice that it says OB and OC are arcs of circles.


Original post by SM45367
Same question was posted 3 days ago:
http://www.thestudentroom.co.uk/showthread.php?p=65004729&highlight=

should be useful^


Thank you so much!!! :biggrin:

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