Question

cos 60cos45 -sin 60 sin 45

Answer 1

cos60.cos45 - sin 60 sin 45
=√3/2.1/√2 -√3/2.1/√2
=0

Answer 2

cos 60°.cos 45° - sin 60°.sin 45°
Given cos 60° = 1/2, cos 45° = 1/√2, sin 60° = √3/2, sin 45° = 1/√2
1/2 * 1/√2 - √3/2 * 1/√2
1/2√2 - √3/2√2
=  1 - √3
    2√2