Posted by **Trig** on Thursday, July 4, 2013 at 4:14pm.

Find all solutions in the interval [0,2pi].

sin 2x + sin x = 0

- trig -
**Damon**, Thursday, July 4, 2013 at 5:25pm
sin 2 x = 2 sin x cos x

2 sin x cos x + sin x = 0

sin x (2 cos x + 1) = 0

so

x = 0 is a solution and x = 180 is a solution

then

cos x = -1/2

that is at x = 120 and x = 240

- trig -
**Reiny**, Thursday, July 4, 2013 at 9:45pm
We should also include 360° , (from sinx = 0)

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