Posted by **Abby** on Saturday, March 6, 2010 at 6:12pm.

Approximate the equation's soultions in the interval (o, 2pi). If possible find the exact solutions.

sin 2x sinx = cosx

I do not know where to start.

- Pre-Cal -
**MathMate**, Saturday, March 6, 2010 at 11:15pm
Expand sin 2x using the identity:

sin2x=2sin(x)cos(x)

We'll get:

2cos(x)sin²(x)=cos(x)

Transpose left-hand-side to the right:

2cos(x)((1/2)-sin²(x))=0

So

cos(x)=0, or

sin²(x)=1/2

Solve for x in (0,2π) as specified.

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