hitunglah cos 60°×cos 45°+sin60°×sin 45°

cos60°cos45°+sin60°sin45° = cos(60°-45°) = cos15° = 1/4(√2+√6)

cos 60° cos 45° + sin 60° sin 45°
= 1/2 . 1/2 √2 + 1/2 √3 . 1/2 √2
= 1/4 √2 + 1/4 √6

= 1/4 (√2 + √6)

= 1/4 √2 (1 + √3)