dfrac (pi )(4) C. dfrac (pi )(2) D.π
dfrac (q)(4pi varepsilon oR)-|||-C. dfrac (q)(4pi {varepsilon )_(0)(R)^2}-|||-D.
sqrt (2)pi -|||-C. dfrac (sqrt {2pi )}(4)-|||-D. dfrac (sqrt {2pi )}(8)
dfrac (qQ)(4pi {varepsilon )_(0)l} C. dfrac (qQ)(2pi {varepsilon )_(0)l} D. -dfr
[ 0,dfrac (pi )(2)] D. [ -sqrt (dfrac {pi )(2)},0]
dfrac (qQ)(4pi {varepsilon )_(0)(d)_(1)} B. dfrac (qQ)(2pi {varepsilon )_(0)(d)_
-dfrac (1)(pi )-|||-D. dfrac (1)(pi )
3.要使函数φ(x )= ,dfrac {pi )(2)] (B)[π,2π] (C) [ 0,dfrac (pi )(2)] (D) [ dfrac
(B) pi +dfrac (4)(3) (C) pi +2 . (D) pi +dfrac (8)(3)
(B) dfrac (lambda )(2pi {varepsilon )_(0)a}. (C) dfrac (lambda )(4pi {varepsilon