F(x)=∫Acosxdx|[-π/2,π/2]=1
∫Acosxdx
=A∫cosxdx
=Asinx+C
F(x)=∫Acosxdx|[-π/2,π/2]
=sin(π/2)-sin(-π/2)
=A-(-A)
=2A=1
∴A=1/2
P(0