chapter 10 trig identity and equations | Revision Server | Page 1

simple sparrow Nov 28, 2022, 7:05 PM

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How to do B graphical method (not CAST) <@&791435371564892232>

rotund cradleBOT Nov 28, 2022, 7:06 PM

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versed sail Nov 28, 2022, 7:09 PM

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hi

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what did you get for A

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do 180 - that

simple sparrow Nov 28, 2022, 7:10 PM

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versed sail do 180 - that

That would give you the wrong answer

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I'll show you what i did but its wrong

versed sail Nov 28, 2022, 7:11 PM

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simple sparrow

is part A right

simple sparrow Nov 28, 2022, 7:11 PM

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Yes

versed sail Nov 28, 2022, 7:11 PM

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whats ur answer for part A

simple sparrow Nov 28, 2022, 7:11 PM

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It's just a show that Q

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sinQ = 2/3

versed sail Nov 28, 2022, 7:11 PM

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oh ok

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so

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so sin(2/3)

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180 - answer

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then cos(answer)

simple sparrow Nov 28, 2022, 7:12 PM

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that gives you -0.99999

versed sail Nov 28, 2022, 7:12 PM

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cos Q is -0.745

versed sail Nov 28, 2022, 7:13 PM

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simple sparrow that gives you -0.99999

sin inverse 2/3

simple sparrow Nov 28, 2022, 7:13 PM

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41.8

versed sail Nov 28, 2022, 7:13 PM

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180-41.8

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= 138.2

simple sparrow Nov 28, 2022, 7:13 PM

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138.18

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yeah

versed sail Nov 28, 2022, 7:13 PM

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cos(138.2)

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=

simple sparrow Nov 28, 2022, 7:13 PM

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-0.74

versed sail Nov 28, 2022, 7:14 PM

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thats it

simple sparrow Nov 28, 2022, 7:14 PM

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I'm confused

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One sec

simple sparrow Nov 28, 2022, 7:16 PM

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versed sail 180-41.8

why did you do use 180?

versed sail Nov 28, 2022, 7:16 PM

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simple sparrow why did you do use 180?

because sine graph is symmetrical

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you just have to know

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if you want to find the other angle with same value

simple sparrow Nov 28, 2022, 7:17 PM

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yeah

versed sail Nov 28, 2022, 7:17 PM

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you minus by 180

simple sparrow Nov 28, 2022, 7:17 PM

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180 - x

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BUT

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Aren't we using cos, hence it would be 360?

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versed sail Nov 28, 2022, 7:18 PM

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no

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the sine angle of that question is 41.8

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so use the sine rule not cosine

simple sparrow Nov 28, 2022, 7:20 PM

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oh right makes sense

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wait so isnt the mark scheme wrong

versed sail Nov 28, 2022, 7:22 PM

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whats the markscheme saying

simple sparrow Nov 28, 2022, 7:25 PM

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well we found that cosQ=-0.74,
but mark scheme says that cosQ=root5/3 which is 0.9999

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@versed sail

simple sparrow Nov 28, 2022, 8:11 PM

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anyone have any idea?

#chapter 10 trig identity and equations