SOLUTION: What are the possible values of x domain: [0,2pi). 4sin^3(x) + 2sin^2(x) = 2sin(x) + 1 So far I've: set equal to zero: 4sin^3(x) + 2sin^2(x) + 2sin(x) + 1 = 0

Algebra ->  Trigonometry-basics -> SOLUTION: What are the possible values of x domain: [0,2pi). 4sin^3(x) + 2sin^2(x) = 2sin(x) + 1 So far I've: set equal to zero: 4sin^3(x) + 2sin^2(x) + 2sin(x) + 1 = 0      Log On


   



Question 381159: What are the possible values of x domain: [0,2pi).
4sin^3(x) + 2sin^2(x) = 2sin(x) + 1
So far I've:
set equal to zero:
4sin^3(x) + 2sin^2(x) + 2sin(x) + 1 = 0

Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
First of all when you set everything equal to zero you should obtain
4+sin%5E3+%28x%29+%2B+2+sin%5E2+%28x%29+-+2+sin+x+-+1+=+0
Let a = sin x. The equation then becomes
4a%5E3+%2B+2a%5E2+-+2a+-+1+=+0
This is equivalent to 4a%5E3+-+2a+%2B+2a%5E2+-+1+=+0. We can factor 2a%5E2+-1 to obtain
%282a%5E2+-+1%29%282a+%2B+1%29+=+0
Solving, we obtain a = -1/2, sqrt(2)/2, and -sqrt(2)/2. All of these values are between -1 and 1, so we can find sin^-1 of each of these angles to find all values for x:
sin%5E%28-1%29+%28-1%2F2%29+=+%287pi%2F6%29 or %2811pi%2F6%29

sin%5E%28-1%29+%28sqrt%282%29%2F2%29+=+pi%2F4 or 3pi%2F4

sin%5E%28-1%29+%28-sqrt%282%29%2F2%29+=+5pi%2F4 or 7pi%2F4