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*HELP* Finding x in [_,_] of Possible Inflection Points

by AnnaSuxCalc
Tags: inflection, points
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AnnaSuxCalc
#19
Jan15-09, 09:15 PM
P: 55
Quote Quote by NoMoreExams View Post
You would use your calculator and type in arcsin(.618)?
haha, yes I did taht but it only gives me the one value of x, but there are two intersections so there is another value of x that gives sin(x) = 0.6180
if you just do sin-1 (0.6180) = 0.6662 ---> only one value, i need 2 values
NoMoreExams
#20
Jan15-09, 09:18 PM
P: 626
OK let's pick a simpler example. If you had to find sin(x) = 1/2 how would you figure out x?
AnnaSuxCalc
#21
Jan15-09, 09:19 PM
P: 55
Quote Quote by NoMoreExams View Post
OK let's pick a simpler example. If you had to find sin(x) = 1/2 how would you figure out x?
sin-1(1/2) = x
NoMoreExams
#22
Jan15-09, 09:20 PM
P: 626
lol sure, but if you didn't have a calculator, how would you figure that one out.
AnnaSuxCalc
#23
Jan15-09, 09:24 PM
P: 55
Quote Quote by NoMoreExams View Post
lol sure, but if you didn't have a calculator, how would you figure that one out.
oh you got me i dont know
NoMoreExams
#24
Jan15-09, 09:26 PM
P: 626
You should go back and review trigonometry. It's on the unit circle.
AnnaSuxCalc
#25
Jan15-09, 09:34 PM
P: 55
come on help me out here (your name), lol ok fine soooo...
sinθ = y/r --> y=1 and r=2 using THE theorem x=sqrt3 ???
NoMoreExams
#26
Jan15-09, 09:37 PM
P: 626
You can look the answer up on wikipedia, it's a common angle and it was already addressed in this thread I believe.
AnnaSuxCalc
#27
Jan15-09, 09:49 PM
P: 55
okay Im not sure what your getting at, I know that sin(π/6) = 1/2 and sin(5π/6) = 1/2
NoMoreExams
#28
Jan15-09, 09:56 PM
P: 626
I'm trying to get you to remember how those values were determined. Sin(pi/6) = 1/2 is easy. So we know 30 degrees is what we need. Since we have sine, it's positive in 1st and 2nd quadrants. So in the first quadrant we have 30 degrees, in the 2nd we know our "line" must make a 30 degree angle with the horizontal which would be pi, so we did pi - pi/6 = 5pi/6
AnnaSuxCalc
#29
Jan15-09, 10:02 PM
P: 55
oh ok so my number is not 1/2 but 0.6180 so that is 38.17degrees
so the line must make a 38.2degree angle with the horizontal since pi is (180degrees)
180-38.2 = 141.2degrees ~2.46rad
is this the answer?
NoMoreExams
#30
Jan15-09, 10:06 PM
P: 626
Well try plugging that into your calculator :)
AnnaSuxCalc
#31
Jan15-09, 10:14 PM
P: 55
Quote Quote by NoMoreExams View Post
Well try plugging that into your calculator :)
Yay
NoMoreExams
#32
Jan15-09, 10:14 PM
P: 626
There you go champ :)
AnnaSuxCalc
#33
Jan15-09, 10:17 PM
P: 55
thanks (still didnt tell me your name) :) now i just have to finish the rest of the assignment lol
NoMoreExams
#34
Jan15-09, 10:20 PM
P: 626
The beauty of the anonymity of the Internetz ;-)
AnnaSuxCalc
#35
Jan15-09, 10:22 PM
P: 55
Quote Quote by NoMoreExams View Post
The beauty of the anonymity of the Internetz ;-)
haha okay Genius, thanks for the help
NoMoreExams
#36
Jan15-09, 10:23 PM
P: 626
Genius - far, far, far from it but you are welcome.


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