solve each equation on the interval 0<data<2pi

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alyren

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solve each equation on the interval 0<data<2pi

cos(2data) - cos (4 data)= 0

no idea how to solve this, first i try using double angle identities : cos(2data) = 2cos^2-1. but what do i need for the cos(4data)?
 
alyren said:
solve each equation on the interval 0<data<2pi

cos(2data) - cos (4 data)= 0

no idea how to solve this, first i try using double angle identities : cos(2data) = 2cos^2-1. but what do i need for the cos(4data)?
Click to expand...

\(\displaystyle cos(4\theta) = 2cos^2(2\theta) - 1\)
 
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