Răspuns:
£ = alfa
1) £ = 0°
a × b = ab × cos £
a × b = 3 × 9 × cos 0°
a × b = 27 × 1 = 27
2) £ = 30°
a × b = ab × cos £
a × b = 3 × 9 × cos 30°
a × b = 27 × (radical din 3)/2
3) £ = 60°
a × b = ab × cos £
a × b = 3 × 9 × cos 60°
a × b = 27 × 1/2
a × b = 13,5
4) £ = 90°
a × b = ab × cos £
a × b = 3 × 9 × cos 90°
a × b = 27 × 0 = 0
5) £ = 45°
a × b = ab × cos £
a × b = 3 × 9 × cos 45°
a × b = 27 × (radical din 2)/2
