Bonjour pouvez vous m’aidez pour l’exercice 3 svp.

Réponse :

a) sinx = 1/2 => x = π/6 + k2π   ou x = 5π/6 + k2π

b) 2cosx + 1 = 0 => cosx = -1/2 => x= ± 2π/3 + k2π

c) cos3x = sin2x => cos3x = cos(π/2 - 2x) => 3x = ±(π/2 - 2x) + k2π

1° 3x = π/2 - 2x + k2π => 5x = π/2 + k2π => x = π/10 + k2π/5 (5 solutions)

2° 3x = -π/2 +2x + k2π => x = -π/2 +k2π

Bonne journée

Explications étape par étape