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Use the equation twice to find cos(15) if it known that cos(60)=0.5
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You need to use the formula of half angle such that:
`cos (alpha/2) = sqrt ((1 +cos alpha)/2)`
You have recommended to use the cosine of the angle of `60^o` .
`cos 30^o = cos (60^o/2) = sqrt ((1 + cos 60^o)/2)`
`cos 30^o = cos (60^o/2) = sqrt ((1 + 0.5)/2)`
`cos 30^o = cos (60^o/2) = sqrt ((1.5)/2)`
`cos 15^o = cos (30^o/2) = sqrt ((1 + sqrt ((1.5)/2))/2)`
`cos 15^o~~` 0.965
The value of cos `15^o` `~~` 0.965.
Posted by sciencesolve on December 12, 2011 at 4:43 PM (Answer #1)
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