2xcos45° / 1-(sin 45°)²

2(cos45) / 1 - (sin45)²

= 2 (1/2 √2) / 1 - (1/2 √2)²
= √2 / 1 - 1/4 (2)
= √2 / 1 - 1/2
= √2 / 1/2
= 2√2

→ Atau menggunakan identitas :
[ cos 45 = x ]

2(cos45) / 1 - (sin45)²
→ 2 (cosx) / 1 - sin²x

= 2cosx / 1 - sin²x
= 2cosx / cos²x
= 2 / cosx
= 2 / cos45
= 2 / 1/2√2
= 2 / √2 / 2
= 2 x (2 / √2)
= 4 / √2
= 4√2 / √2 . √2
= 4√2 / 2
= 2√2