Răspuns:
Explicație pas cu pas:
sin²x+cos²x=1
cos²x=1-sin²x
cos²x=1-(2/3)²=1-4/9=(9-4)/9=5/9
cos x = ±√(5/9) = ±√5 / 3
x∈(π/2 , π) ⇒cos x <0
⇒cos x = -√5/3
tg x = sin x /cos x = (2/3) / (-√5/3) = - 2/3 * 3/√5= - 2/√5 = -2√5/5
ctg x = cos x /sin x= (-√5/3)/(2/3)= -√5/3*2/3= -√5/2
