Math Help - Solving trigonometric equations:

1. Solving trigonometric equations:

Solve for .

Here's my work:
sin(x) + sin(2x) = 0
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what do I do now? I can't think of any trig identities or anything to simplify it? Do i just do sin(x) = - sin(2x) which obviously isn't true, does anyone know??

2. Re: Solving trigonometric equations:

Your pictures are broken. Try using Imageshack or some free image hosting. Or you can also upload to MHF, now that pictures appear to be working again.

3. Re: Solving trigonometric equations:

Sorry about that, the picture is solve for sin(x) + 2*sin(x)*cos(x) = 0 for 0 degrees <= x < 180 degrees
I used a double angle idendtity to reduce from the aforementioned equation to sin(x) + sin(2x) = 0

4. Re: Solving trigonometric equations:

Originally Posted by glambeth
Sorry about that, the picture is solve for $\sin(x) + 2\sin(x)\cos(x) = 0$ for 0 degrees <= x < 180 degrees
Factor $\sin(x)[1+2\cos(x)]=0$ so
$\sin(x)=0~\text{ or }~\cos(x)=-\frac{1}{2}$.

5. Re: Solving trigonometric equations:

I see now, so x is equal to 0, 120, or 180?

6. Re: Solving trigonometric equations:

since x is strictly less than 180 degrees you should not take that as the answer.

7. Re: Solving trigonometric equations:

Thanks, no idea how I missed that!