Please Help

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Find all solutions in the interval [0,2pi): cos2x+sinx=0 please help :cry:
 
Use the double-angle identity to convert cos(2x) into an expression only using sines. This will give you a quadratic in sin(x). Solve for the values of sin(x), and then solve the resulting equations for x.

Eliz.
 
If you're covering this sort of material, then you should have covered (and memorized) the basic identities, such as the half-angle identities and the double-angle identities. Otherwise, there is no way (that I'm aware of) to solve the equation.

Check your book, in the sections recently covered, or look in the back for the pages where "identities" are covered. You should find a listing of them.

Eliz.
 
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