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Trig Help

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madchronic
Posts: 460 - Karma: 324
Hey I usually never do this but this problem is bugging the shit out of me.
Can anyone post how to get
cos [sin^(-1)(2/3)+2 sin^(-1)(-1/3)]
I believe it's basically asking for cos(a+2b) but I can't get to the right answer
((8 sqrt(2))/27+(7 sqrt(5))/27)
Oct 26 2016 9:46PM
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DirtYStylE
Posts: 3652 - Karma: 8,888
Trigg and proffs are the cancer and aids of math. I will not help you with this. Sorry, not sorry.

You should try this instead of ns: wolframalpha.com
Oct 26 2016 9:50PM
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madchronic
Posts: 460 - Karma: 324
DirtYStylETrigg and proffs are the cancer and aids of math. I will not help you with this. Sorry, not sorry.

You should try this instead of ns: wolframalpha.com

I know haha. I don't have wolfram alpha pro so it only gives the answer not the actual steps.
Oct 26 2016 10:11PM
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DirtYStylE
Posts: 3652 - Karma: 8,888
madchronicI know haha. I don't have wolfram alpha pro so it only gives the answer not the actual steps.


back in my day the skies were blue and that was free. rip
Oct 26 2016 10:19PM
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DirtYStylE
Posts: 3652 - Karma: 8,888
https://www.khanacademy.org/math/trigonometry
Oct 26 2016 10:21PM
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Iraq_Lobster
Posts: 1866 - Karma: 4,904
depends, what level of trig is this. HS or college
Oct 26 2016 10:56PM
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madchronic
Posts: 460 - Karma: 324
Iraq_Lobsterdepends, what level of trig is this. HS or college

HS
Oct 26 2016 10:58PM
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madchronic
Posts: 460 - Karma: 324
Iraq_Lobsterdepends, what level of trig is this. HS or college

The answer is
((8 sqrt(2))/27+(7 sqrt(5))/27)

I just don't know how to get that
Oct 26 2016 11:00PM
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Iraq_Lobster
Posts: 1866 - Karma: 4,904
madchronicThe answer is
((8 sqrt(2))/27+(7 sqrt(5))/27)

I just don't know how to get that


wow it's been a lot longer than I thought than. Sorry, I don't think my trig skills are up to date
Oct 26 2016 11:05PM
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madchronic
Posts: 460 - Karma: 324
Iraq_Lobsterwow it's been a lot longer than I thought than. Sorry, I don't think my trig skills are up to date

All good. It's not your average trig, my teacher pulls crazy questions from princeton,stanford, etc.
Oct 26 2016 11:10PM
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McNoche
Posts: 1731 - Karma: 3,661
How in sam fuck does an 8 come into play?
Oct 26 2016 11:30PM
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djikstra
Posts: 2471 - Karma: 6,014
Are you allowed to use your graphing calculator or do you need to do it all by hand? if you start from the inside out you can start with sin^-1(2/3) is sin(x) = 2/3 solve for x basically, same with the -1/3. Assuming you're allowed your graphing calculator that gives you: sin^-1(2/3) = .72972766 rads. sin^-1(-1/3) = -.33983691 rads. .72972755 + 2(-.33983691) = .05005384. take the cos() of that and you'll get ((8 sqrt(2))/27+(7 sqrt(5))/27) in decimal form which is .99874757. If you need to solve it by hand without using the inverse sin function button on your calculator then your highschool trig is harder than college level trig... hope that helps!
Oct 28 2016 1:43AM
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Carl_the_Llama
Posts: 504 - Karma: 1,295
LJAre you allowed to use your graphing calculator or do you need to do it all by hand? if you start from the inside out you can start with sin^-1(2/3) is sin(x) = 2/3 solve for x basically, same with the -1/3. Assuming you're allowed your graphing calculator that gives you: sin^-1(2/3) = .72972766 rads. sin^-1(-1/3) = -.33983691 rads. .72972755 + 2(-.33983691) = .05005384. take the cos() of that and you'll get ((8 sqrt(2))/27+(7 sqrt(5))/27) in decimal form which is .99874757. If you need to solve it by hand without using the inverse sin function button on your calculator then your highschool trig is harder than college level trig... hope that helps!


When LJ is a math wizard and a ski god
Oct 28 2016 1:47PM
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Deezy
Posts: 4580 - Karma: 1,004

Hope this helps, op

First, I would use any rules you know to break up the identites and then pull it all apart using the laws above.

i have an exam rn ill do it after if i have time and nobody ele has done it

goodluck
Oct 28 2016 2:06PM
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