Jawabanmu

2014-06-23T21:33:19+07:00
Α+β=180/6
cos(α+β)=cos (180/6)
cosαcosβ-sinαsinβ= \frac{ \sqrt{3} }{2}
3/4-sinαsinβ= \frac{ \sqrt{3} }{2}
3/4- \frac{ \sqrt{3} }{2} =sinαsinβ
 \frac{1}{4}( 3-2 \sqrt{3})  =sinαsinβ

cos(α-β)
cosαcosβ+sinαsinβ=3/4+ \frac{1}{4}( 3-2 \sqrt{3})
= \frac{1}{4} (6- 2\sqrt{3} )