3. F(x)=∫(x⁻³+cosx)dx=x⁻⁴/(-4)+sinx+c=-x⁻⁴/4+sinx+c
F(0.5π)=-(0.5π)⁴/4+sinπ/2+c=-1/(2π²)
-π⁴/64+0+c=-1/(2π²)
c=-1/(2π²)+π⁴/64

F(x)=-x⁻⁴/4+sinx-1/(2π²)+π⁴/64