How do you solve $2cos(2x+80)=1$ for $0<=x<=pi$ ?

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Answer 1 · 2016-08-25T15:38:50

$125deg$ and $170deg$

$2cos(2x+80)=1$
$cos(2x+80)=1/2$

The angle whose cos is $1/2$ is 60

Draw the cosine graph ( I don't know how to do that on this)

The other angles whose cos is 60 are 330 and 450...etc

$2x+80=60$ that gives x = -10 not in range
$2x+80=330$ that gives x =125 that's ok
$2x+80=420$ that gives x= 170 that's ok

How do you solve 2cos(2x+80)=12cos(2x+80)=1 for 0<=x<=pi0<=x<=pi?