# A level maths pure Watch

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Hey stuck on some questions would appreciate some help .im on a roll today with questions .could someone explain working out to part b on first attachment.

Last edited by abbeygyal23; 1 month ago

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#2

(Original post by

Hey stuck on some questions would appreciate some help .im on a roll today with questions .could someone explain working out to part b on first attachment.

**abbeygyal23**)Hey stuck on some questions would appreciate some help .im on a roll today with questions .could someone explain working out to part b on first attachment.

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#3

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you just gotta split the shape up into its components , so first you have 2 rectangles of dimensions( the sides of the diagram) 10 x 20 , so 10x20x 2= 400 the bit without the pi in what you need to reach. then you have x2 the the area of the sector which is ( ((pi/4)/2pi) x pi x 20squared) ( x 2 cuz 2 of them on the botttom and top) which gives you 100 pi , then you also have the the curved edge of this "slice of cake" , you get this from arc length x height , so (2x pi x 20 x ((pi/4)/2pi)) x 10 = 50 pi which you add to the previous areas to get 400 + 150 pi as required

**burntcherrio**)you just gotta split the shape up into its components , so first you have 2 rectangles of dimensions( the sides of the diagram) 10 x 20 , so 10x20x 2= 400 the bit without the pi in what you need to reach. then you have x2 the the area of the sector which is ( ((pi/4)/2pi) x pi x 20squared) ( x 2 cuz 2 of them on the botttom and top) which gives you 100 pi , then you also have the the curved edge of this "slice of cake" , you get this from arc length x height , so (2x pi x 20 x ((pi/4)/2pi)) x 10 = 50 pi which you add to the previous areas to get 400 + 150 pi as required

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#4

for the trig questions you need to be able to use relationships confidently...

Sin2Θ

cos

tanΘ

can all be written in other ways.

Sin2Θ

cos

^{2}ΘtanΘ

can all be written in other ways.

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**burntcherrio**)

you just gotta split the shape up into its components , so first you have 2 rectangles of dimensions( the sides of the diagram) 10 x 20 , so 10x20x 2= 400 the bit without the pi in what you need to reach. then you have x2 the the area of the sector which is ( ((pi/4)/2pi) x pi x 20squared) ( x 2 cuz 2 of them on the botttom and top) which gives you 100 pi , then you also have the the curved edge of this "slice of cake" , you get this from arc length x height , so (2x pi x 20 x ((pi/4)/2pi)) x 10 = 50 pi which you add to the previous areas to get 400 + 150 pi as required

__2pi)x pi x20squared.__The underlined bit is the bit I don't really get. With the curved edge is this not part of the area of 100pi?Sorry I'm just confused

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(Original post by

( ((pi/4)/2pi) refers to the fraction of pi/4 of the whole circle of 2 pi

**burntcherrio**)( ((pi/4)/2pi) refers to the fraction of pi/4 of the whole circle of 2 pi

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#7

(Original post by

Oh okay I understand the 2PI bit now but after this?

**abbeygyal23**)Oh okay I understand the 2PI bit now but after this?

2x area of sector = 2*50*pi=100pi

Area formed by arc = length of arc * height = 20*pi/4 *10 = 50pi

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#8

(Original post by

Oh okay I understand the 2PI bit now but after this?

**abbeygyal23**)Oh okay I understand the 2PI bit now but after this?

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#9

(Original post by

2x area of rectangle = 400

2x area of sector = 2*50*pi=100pi

Area formed by arc = length of arc * height = 20*pi/4 *10 = 50pi

**vbzl**)2x area of rectangle = 400

2x area of sector = 2*50*pi=100pi

Area formed by arc = length of arc * height = 20*pi/4 *10 = 50pi

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#10

**vbzl**)

2x area of rectangle = 400

2x area of sector = 2*50*pi=100pi

Area formed by arc = length of arc * height = 20*pi/4 *10 = 50pi

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(Original post by

here is a ms paint diagram, that should help visualize this

**burntcherrio**)here is a ms paint diagram, that should help visualize this

Much!!!!! I am a visual person so this really helped with clarity !!!!!!

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