diket sin 5=x dan cos 5=y maka sin 40

Sin5=x
Cos5=y
Sin40 = sin(45-5)

Sin(45-5) = sin45cos5-cos45sin5
Sin(40)= √2/2.y-√2/2.x
= √2/2(y-x)
= -√2/2(x-y)

Ket : √2/2 = setengah akar 2
Semoga bermanfaat dan tdk trlamabar