Jawabanmu

Jawaban paling cerdas!
2014-06-23T20:40:18+07:00
Cos2x-cosx+1=0
(cos²x-sin²x)-cosx+1=0
(cos²x-(1-cos²x))-cosx+1=0
cos²x-1+cos²x-cosx+1=0
2cos²x+-cosx=0....
2cos²x=cosx
agap aja cosx=p
2p²=p
2p=1
p=1/2
cosx=1/2
nilai x yang memenuhi=  60^{o} dan  300^{o}

cos  75^{o} = cos(30+45)
cosαcosβ-sinαsinβ=cos(α+β)
cos30cos45-sin30sin45= (\frac{ \sqrt{3} }{2})( \frac{ \sqrt{2} }{2})- (\frac{1}{2})( \frac{ \sqrt{2} }{2} )=  \frac{ \sqrt{6} }{4}- \frac{ \sqrt{2} }{4}= \frac{1}{4}( \sqrt{6} -  \sqrt{2})
yg pertama gak ada jawabannya bang :)