Diketahui α + β = 60° dan sin α sin β = 1/4, maka cos ( α - β )?

[tex]Trigonometri[/tex]

cos (α+β) = cosαcosβ - sinαsinβ
cos π/3 = cosαcosβ - ¼
½ = cosαcosβ - ¼
¾ = cosαcosβ

cos (α-β) = cosαcosβ + sinαsinβ
= cosαcosβ + ¼
= ¾ + ¼
= 1 ✔️

semoga jelas dan membantu