1-(sin 30°)² / 1+(sin 30°)²

1 - (sin30)² / 1 + (sin30)²

= 1 - (1/2)² / 1 + (1/2)²
= 1 - 1/4 : 1 + 1/4
= 3/4 : 5/4
= 3/5

→ Atau menggunakan identitas :
[ 30˚ = x ]

1 - (sin30)² / 1 + (sin30)²
→ 1 - sin²x / 1 + sin²x

= cos²x / 1 + sin²x
= (1/2 √3)² : 1 + 1/2²
= 1/4 . 3 : 1 + 1/4
= 3/4 : 5/4
= 3/5