第1个回答 2021-06-15
f(x)
=sinx ; 0≤x<π
=2 ; π≤x≤2π
F(x) =∫(0->x) f(t) dt
分段考虑
case 1: x<π
F(x)
=∫(0->x) f(t) dt
=∫(0->x) sint dt
=-[cost]|(0->x)
=1- cosx
case 2: π≤x≤2π
F(x)
=∫(0->x) f(t) dt
=∫(0->π) f(t) dt + ∫(π->x) f(t) dt
=∫(0->π) sint dt + ∫(π->x) 2 dt
=-[cost]|(0->π) +2[t]|(π->x)
=2 +2x- 2π
ie
F(x)
=1- cosx ; 0≤x<π
=2 +2x- 2π ; π≤x≤2π