SOLUTION: Use trigonometric identities to solve cos(2&#952;)+cos(&#952;)=0 exactly for 0&#8728;&#8804;&#952;<360&#8728;. If there is more than one answer, enter your answers as a comma separ

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Question 869656: Use trigonometric identities to solve cos(2θ)+cos(θ)=0 exactly for 0∘≤θ<360∘. If there is more than one answer, enter your answers as a comma separated list.
Answer by KMST(5328)   (Show Source): You can put this solution on YOUR website!

So,
can be re-written as

and if we abbreviate it by defining
we can re-write it as

That quadratic equation can be solve by factoring,
or by completing the square,
or by using the quadratic formula,
to yield the solutions
.
Going back to and for
we find that --->
and --->

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