Answer:
Step-by-step explanation:
2sin³x - 5sin²x + 2sinx = 0(*)
suppose : sinx = t; t∈[-1;1]
(*)⇔ 2t³ - 5t² +2t = 0
⇔ t.(2t² - 5t +2) = 0
⇔ t( t -2)(2t -1) = 0
⇔ t = 0
t = 2 (unsatisfactory)
t = 1/2
⇔ sin x = 1
sin x = 1/2
⇔ x = pi
x = pi/6
( because 0≤x≤pi)
