Find the general solution to cos2x=-cosx

Caelan 2021-02-11 Answered
Find the general solution to cos2x=cosx
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Expert Answer

jlo2niT
Answered 2021-02-12 Author has 96 answers

cos(2x)=2cos2(x)1
2cos2(x)1=cos(x)
2cos2(x)1cos(x)=0
2cos2(x)cos(x)1=0
(2cos(x)+1)(cos(x)1)=0
2cos(x)+1=0
2cos(x)=1
cos(x)=12
x=cos1(12)
x=π/3[2ππ/3=5π/3]
x=π/3 and 5π/3
cos is positive in the first and fourth quadrant.
cos(x)1=0
cos(x)=1
x=cos1(1)
x=0,2π

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