UPSB v4
Off-topic / math hw help
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Date: Wed, Jun 22 2011 08:55:31
find the value of x in degrees 1. √3 csc x -2 =0 2. sin²x = 1/2 3. tan(x-1) = √3 4. cos²x - sin²x+sinx=1 5. 2cosx - 2secx=3 6. 2cos²x + 9cosx - 5 = 0 7. 2sinx + secx = 0 8. 1 - tan²x = tanxsecx need help thx, its ok if you dont answer 3, we were asked to skip it, but if you can answer it then pls do, i don't really need answers in degrees... we have the chart of the equivalent degrees of the answers like √3/3 = 60 degrees or something...so if you get the answer as √3/3 or √2/2 or something it's ok, ill do the conversion, thx, badly need to pass the 1st term and get high grades to enter college
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Date: Wed, Jun 22 2011 11:53:03
1) 1/sin x = 2/√3 ->>> sin x = √3/2 -> x = 60 degrees and x = 120 degrees 2) sin x = + 1/4 ->>> x = arcsin 1/4 AND sin x = -1/4 ->> x = arcsin -1/4 (There are more answers. You are going to have to use the circle and find the other answers.) 3) x-1 = 60 degrees. ->>> x = 61 degrees 4) 1 - 2sin²x + sin x = 1 -->>> - 2sin²x + sin x = 0 -->>> sin x = 0 -->> x = k(180 degrees)(idk, i am used to saying k(pi) cuz i work in radians) AND sin x = 1/2 -->>> x = 30 degrees and 150 degrees. Ill do the rest after i get back from school. #8 is actually really easy. cos²x - 2sin²x / cos²x = 0 There is going to be a restriction. cos²x =/= 0. x =/= 90 or 270 degrees. so then we get 2tan²x = 1 -->>> tan²x = 1/2 -->>> tan x = 1/4 ->>> x = arctan 1/4. (Check the other answers on the circle.) Do your homework...They are pretty easy
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Date: Wed, Jun 22 2011 12:23:38
THANK YOU YOU ARE MY HERO
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Date: Wed, Jun 22 2011 17:11:02
oh god i hate trig
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Date: Wed, Jun 22 2011 17:54:58
O shit Im taking this stuff next year.....
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Date: Wed, Jun 22 2011 23:20:58
Do i has to do teh rest or did u do them?
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Date: Thu, Jun 23 2011 00:09:28
Just to let you know, @Clyde, Hex only gave you answers restricted to 0 ≤ x < 360°. There are actually an infinite number of solutions. If you want all of them, you'll need to add all multiples of 360° to the end of your solutions. For example, x=60° would need to be x=60°+360°k (where k is an integer). Oh, and he did at least one wrong.
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Date: Thu, Jun 23 2011 00:11:52
@nateiskewl for a lot of them even adding 360 doesn't get all the answers. for example sinx=0 is true every 180 degrees not just 360
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Date: Thu, Jun 23 2011 00:39:44
strat1227 wrote: @nateiskewl for a lot of them even adding 360 doesn't get all the answers. for example sinx=0 is true every 180 degrees not just 360
I know that. I was just giving him an easy way to fix the answers. -
Date: Thu, Jun 23 2011 01:11:11
I have no life.
Spoiler
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Date: Thu, Jun 23 2011 01:18:48
@nateiskewl what i'm saying is that what you said won't help him if they want all the answers ... just adding 360*t doesn't do that most of the time
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Date: Thu, Jun 23 2011 01:22:06
strat1227 wrote: @nateiskewl what i'm saying is that what you said won't help him if they want all the answers ... just adding 360*t doesn't do that most of the time
If you know all the solutions with a degree restriction, all you have to do is add on a +360k to each answer to get all of them. -
Date: Thu, Jun 23 2011 01:25:04
again that's not always true, what if the degree restriction is -pi
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Date: Thu, Jun 23 2011 01:27:14
strat1227 wrote: again that's not always true, what if the degree restriction is -pi
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Date: Thu, Jun 23 2011 01:28:11
oh you just said "a degree restriction" either way this is the only real solution
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Date: Thu, Jun 23 2011 01:42:37
strat1227 wrote: @nateiskewl for a lot of them even adding 360 doesn't get all the answers. for example sinx=0 is true every 180 degrees not just 360
I think i did that for the ones that could be done. Nate, I might not be wrong. unless you mean the number of answers. then yea. Idk, i did these in my head. LOL strat. I think nate is right tho. If we have sin x = 0 x = pi/2 + k(pi) , where kEz so for k = 0, x = pi/2 so for k = 1, x = 3pi/2 . . . thus giving us an infinite amount of solutions. UNLESS we restrict 0 < x < 2pi then we would only have 2 answers. -
Date: Thu, Jun 23 2011 02:02:46
uh ... i didn't really understand much of that post, but i can tell you that the solution of sinx=0 is not pi/2 ... that's cosx lol either way trig isn't actually math it's just learning the language that math speaks in upper level classes it's like learning numbers over again, when you learned to count you weren't actually doing math, just learning the things you need for math, trig is the same way
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Date: Thu, Jun 23 2011 03:15:01
Clyde wrote: 5. 2cosx - 2secx=3 6. 2cos²x + 9cosx - 5 = 0 7. 2sinx + secx = 0 8. 1 - tan²x = tanxsecx
#5 and #6 are quadratic equations that can be solved by factoring (convert secx to 1/cosx in#6 first). #7 use the trig identity: 2sinxcosx = sin(2x) #8 use the trig identity: tan²x + 1 = sec²x -
Date: Thu, Jun 23 2011 08:45:24
@all thx, good thing we didn't check it. Our teacher told us we aren't really supposed to be able to answer the other #'s because we didn't take them last year, and special thank @Nate