tan2x=[tex] \sqrt{3} [/tex] (sans calculatrice) 5cosx=7(avec calculatrice) 2sin(x+[tex] \frac{\pi}{4} [/tex]=[tex] \frac{1}{2} [/tex]

tan2x = V3 => 2x = 60° + kpi => x = 30° = kpi/2
x1 = 30° + k2pi ; x2 = 120° = k2pi ; x3 = 210° + k2pi ; x4 = 300° + k2pi

cosx = 7/5 pas possible car -1 < cosx < 1

2sin(x+= => cos (x + pi/4) = 1/4 => x+ pi/4 = + ou - 1,318 + k2pi
=> x = 1,318 - pi/4 = 0,532 + k2pi
=> x = - 1,318 - pi/4= -2,1 + k2pi