Question

Calculati sin 9° cos 36° + sin 36° cos 9°

Answer 1

sin(α+β) = sinαcosβ + cosαsinβ
sin9°cos36° + cos9°sin36° = sin(9°+36°) = sin 45° = √2 /2

Answer 2

sin(a)cos(b) + cos(a)sin(b) = sin(a+b)

sin(9°)cos(36°) + cos(9°)sin(36°) = sin(9°+36°) = sin (45°) = $\frac{ \sqrt{2}} {2}$