#1
2sin^2x = cosx + 1

i need to solve for X. the answers are 60, 180, and 360 but i need to know how because i have to test over this tomorrow and I can't do it =[
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#2
theres such thig as algebra 4? Our school only has up to algebra 2. unless your in college or something.
#3
Study and memorize the unit circle. It's odd your doing Trig in an Algebra class, but at the same time its odd there is an Algebra IV at your school.
#4
omg wtf i though it stoped at alg 2. damn i hate math
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#5
Quote by highway62
theres such thig as algebra 4? Our school only has up to algebra 2. unless your in college or something.


in our school, it goes..

Algebra 1, Plane Geometry, Algebra 2/Trigonometry, Algebra 4/Precalc, Calculus.

I don't get it either.
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#6
Quote by elementwood89
Study and memorize the unit circle.


i know the unit circle but how does that help me in THIS problem?
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#8
Quote by DiveRightIn63
in our school, it goes..

Algebra 1, Plane Geometry, Algebra 2/Trigonometry, Algebra 4/Precalc, Calculus.

I don't get it either.



so algebra 4 is just another name for precal? Well we have precal so i guess its the same.
#9
Quote by highway62
so algebra 4 is just another name for precal? Well we have precal so i guess its the same.


i guess.

to the subject, can anyone help?
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#10
Uh, what happened to algebra 3?

Anyway, I have no clue (specifically). This probably won't help you, but all I know about how they relate is if a sine and cosine of two numbers that add up to 90 are multiplied, it equals 1. Maybe you can manipulate that somehow.

Hold on, is that an exponent after the sine?
#11
Obviously your school needs to study their math because they forgot #3.

EDIT: Damn, beat.
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#12
2sin^2x = cosx + 1

Ok, you use the unit circle to find what different values equal when you take sin/cos/tan of them etc. Also look out for identies (cosx + 1.)
#13
sin x / cos x = tan x
cos x / sin x = cot x = 1 / tan x
sec x = 1 / cos x
csc x = 1 / sin x
sin2 x + cos2 x = 1
tan2 x + 1 = sec2 x = 1 / cos2 x
cot2 x + 1 = csc2 x = 1 / sin2 x

I'm too lazy to do the work for you, so use these relationships until you can get a single sin/cos/tan/sec/csc/cot on one side and a number on the other side
#14
Quote by elementwood89
2sin^2x = cosx + 1

Ok, you use the unit circle to find what different values equal when you take sin/cos/tan of them etc. Also look out for identies (cosx + 1.)


cosx+1 = -sinx, right?

thanks
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#15
2sin^2x=cosx+1

using the identity 1=cos^2x+sin^2x

2(1-cos^2x)=cosx+1


2-2cos^2x=cosx+1

2cos^2x+cosx-1=0


if you make y=cosx we have

2y^2+y-1=0


and you solve the polynomial , then you find the values of x with

x=arccos(y)

I'm not completely sure though, make sure you study the trig identities they help a lot
#16
Quote by Ostinattos
2sin^2x=cosx+1

using the identity 1=cos^2x+sin^2x

2(1-cos^2x)=cosx+1


2-2cos^2x=cosx+1

2cos^2x+cosx-1=0


if you make y=cosx we have

2y^2+y-1=0


and you solve the polynomial , then you find the values of x with

x=arccos(y)

I'm not completely sure though, make sure you study the trig identities they help a lot


the answer is supposed to be in degrees
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#17
I didn't know algebra went above 2
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#18
you really need to study

ok so the polynomial was


2y^2+y-1=0

the solutions are y=-1 and y=.5

so since x=arcos(y)


x=180º for y=-1

x=60º for y=.5
#19
thanks dude.. its not that i didn't study its that i wasn't in class the day it was taught and its not a chapter out of the book
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#20
Substitute Sin^2x and it's a cakewalk from there.
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