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**1. The problem statement, all variables and given/known data**

By using the method of undetermined coefficients,find the particular solution of

y''+y'+y=(sin x)^2

**2. Relevant equations**

i know how to determine the particular solution IF it is sin x.

Ex: sin x ====> Asin x + B cos x (particular)

but i wonder how to determine the (sin x)^2

**3. The attempt at a solution**